MiniExcel/README.zh-CN.md

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### 教学视频链接 : [MiniExcel](https://space.bilibili.com/389344584)

----

### 简介

MiniExcel简单、高效避免OOM的.NET处理Excel查、写、填充数据工具。


目前主流框架大多需要将数据全载入到内存方便操作，但这会导致内存消耗问题，MiniExcel 尝试以 Stream 角度写底层算法逻辑，能让原本1000多MB占用降低到几MB，避免内存不够情况。

![image](https://user-images.githubusercontent.com/12729184/113120478-33d59980-9244-11eb-8675-a49651c8af67.png)

### 特点
- 低内存耗用，避免OOM、频繁 Full GC 情况
- 支持`即时`操作每行数据
- 兼具搭配 LINQ 延迟查询特性，能办到低消耗、快速分页等复杂查询  
- 轻量，不需要安装 Microsoft Office、COM+，DLL小于150KB
- 简便操作的 API 风格



### 快速开始

- [导入、读取 Excel](#getstart1)
- [导出 、创建 Excel](#getstart2)
- [模板填充、创建 Excel](#getstart3)
- [Excel Column Name/Index/Ignore Attribute](#getstart4)
- [例子](#getstart5)

### 安装

请查看 [NuGet](https://www.nuget.org/packages/MiniExcel)

### 更新日志

请查看 [Release Notes](docs)

### TODO

请查看 [TODO](https://github.com/shps951023/MiniExcel/projects/1?fullscreen=true)

### 性能比较、测试

Benchmarks  逻辑可以在 [MiniExcel.Benchmarks](benchmarks/MiniExcel.Benchmarks/Program.cs) 查看或是提交 PR，运行指令

```bash
dotnet run -p .\benchmarks\MiniExcel.Benchmarks\ -c Release -f netcoreapp3.1 -- -f * --join
```

最后一次运行规格、结果 :  

```bash
BenchmarkDotNet=v0.12.1, OS=Windows 10.0.19042
Intel Core i7-7700 CPU 3.60GHz (Kaby Lake), 1 CPU, 8 logical and 4 physical cores
  [Host]     : .NET Framework 4.8 (4.8.4341.0), X64 RyuJIT
  Job-ZYYABG : .NET Framework 4.8 (4.8.4341.0), X64 RyuJIT
IterationCount=3  LaunchCount=3  WarmupCount=3  
```

Benchmark History :  [Link](https://github.com/shps951023/MiniExcel/issues/276)


#### 导入、查询 Excel 比较
逻辑 : 以 [**Test1,000,000x10.xlsx**](benchmarks/MiniExcel.Benchmarks/Test1%2C000%2C000x10.xlsx) 做基准与主流框架做性能测试，总共 1,000,000 行 * 10 列笔 "HelloWorld"，文件大小 23 MB


| Library      | Method                       | 最大内存耗用 |         平均时间 |
| ---------------------------- | -------------: | ---------------: | ---------------: |
| MiniExcel | 'MiniExcel QueryFirst'       |       0.109 MB | 0.0007264 sec |
| ExcelDataReader | 'ExcelDataReader QueryFirst' |       15.24 MB | 10.66421 sec |
| MiniExcel  | 'MiniExcel Query'            |        17.3 MB | 14.17933 sec |
| ExcelDataReader | 'ExcelDataReader Query'      |        17.3 MB | 22.56508 sec |
| Epplus    | 'Epplus QueryFirst'          |       1,452 MB | 18.19801 sec |
| Epplus        | 'Epplus Query'               |       1,451 MB | 23.64747 sec |
| OpenXmlSDK | 'OpenXmlSDK Query'           |       1,412 MB | 52.00327 sec |
| OpenXmlSDK | 'OpenXmlSDK QueryFirst'      |       1,413 MB | 52.34865 sec |
| ClosedXml | 'ClosedXml QueryFirst'       |       2,158 MB | 66.18897 sec |
| ClosedXml  | 'ClosedXml Query'            |       2,184 MB | 191.43412 sec |

#### 导出、创建 Excel 比较

逻辑 : 创建1千万笔 "HelloWorld"

| Library            | Method                   | 最大内存耗用 |         平均时间 |
| ------------------------ | -------------: | ---------------: | -----------: |
| MiniExcel | 'MiniExcel Create Xlsx'  |          15 MB | 11.53181 sec |
| Epplus | 'Epplus Create Xlsx'     |       1,204 MB | 22.50971 sec |
| OpenXmlSdk | 'OpenXmlSdk Create Xlsx' |       2,621 MB | 42.47399 sec |
| ClosedXml | 'ClosedXml Create Xlsx'  |       7,141 MB | 140.93992 sec |



### 读/导入 Excel <a name="getstart1"></a>



#### 1. Query 查询 Excel 返回`强型别` IEnumerable 数据 [[Try it]](https://dotnetfiddle.net/w5WD1J)

```csharp
public class UserAccount
{
    public Guid ID { get; set; }
    public string Name { get; set; }
    public DateTime BoD { get; set; }
    public int Age { get; set; }
    public bool VIP { get; set; }
    public decimal Points { get; set; }
}

var rows = MiniExcel.Query<UserAccount>(path);

// or

using (var stream = File.OpenRead(path))
    var rows = stream.Query<UserAccount>();
```

![image](https://user-images.githubusercontent.com/12729184/111107423-c8c46b80-8591-11eb-982f-c97a2dafb379.png)


#### 2. Query 查询 Excel 返回`Dynamic` IEnumerable 数据 [[Try it]](https://dotnetfiddle.net/w5WD1J)

* Key 系统预设为 `A,B,C,D...Z`

| MiniExcel     | 1     |
| -------- | -------- |
| Github     | 2     |

```csharp

var rows = MiniExcel.Query(path).ToList();

// or 
using (var stream = File.OpenRead(path))
{
    var rows = stream.Query().ToList();
                
    Assert.Equal("MiniExcel", rows[0].A);
    Assert.Equal(1, rows[0].B);
    Assert.Equal("Github", rows[1].A);
    Assert.Equal(2, rows[1].B);
}
```

#### 3. 查询数据以第一行数据当Key [[Try it]](https://dotnetfiddle.net/w5WD1J)

注意 : 同名以右边数据为准   

Input Excel :    

| Column1 | Column2 |
| -------- | -------- |
| MiniExcel     | 1     |
| Github     | 2     |


```csharp

var rows = MiniExcel.Query(useHeaderRow:true).ToList();

// or

using (var stream = File.OpenRead(path))
{
    var rows = stream.Query(useHeaderRow:true).ToList();

    Assert.Equal("MiniExcel", rows[0].Column1);
    Assert.Equal(1, rows[0].Column2);
    Assert.Equal("Github", rows[1].Column1);
    Assert.Equal(2, rows[1].Column2);
}
```

#### 4. Query 查询支援延迟加载(Deferred Execution)，能配合LINQ First/Take/Skip办到低消耗、高效率复杂查询

举例 : 查询第一笔数据

```csharp
var row = MiniExcel.Query(path).First();
Assert.Equal("HelloWorld", row.A);

// or

using (var stream = File.OpenRead(path))
{
    var row = stream.Query().First();
    Assert.Equal("HelloWorld", row.A);
}
```

与其他框架效率比较 :  

![queryfirst](https://user-images.githubusercontent.com/12729184/111072392-6037a900-8515-11eb-9693-5ce2dad1e460.gif)

#### 5. 查询指定 Sheet 名称

```csharp
MiniExcel.Query(path, sheetName: "SheetName");
//or
stream.Query(sheetName: "SheetName");
```

#### 6. 查询所有 Sheet 名称跟数据

```csharp
var sheetNames = MiniExcel.GetSheetNames(path);
foreach (var sheetName in sheetNames)
{
    var rows = MiniExcel.Query(path, sheetName: sheetName);
}
```

#### 7. 查询所有栏(列)

```csharp
var columns = MiniExcel.GetColumns(path); // e.g result : ["A","B"...]

or

var columns = MiniExcel.GetColumns(path, useHeaderRow: true); 
// e.g result : ["excel表实际的列名称","excel表实际的列名称"...]

var cnt = columns.Count;  // get column count
```

#### 8. Dynamic Query 转成 `IDictionary<string,object>` 数据

```csharp
foreach(IDictionary<string,object> row in MiniExcel.Query(path))
{
    //..
}

// or 
var rows = MiniExcel.Query(path).Cast<IDictionary<string,object>>(); 
```

#### 9. Query 读 Excel 返回 DataTable

提醒 : 不建议使用，因为DataTable会将数据`全载入内存`，失去MiniExcel低内存消耗功能。

```C#
var table = MiniExcel.QueryAsDataTable(path, useHeaderRow: true);
```

![image](https://user-images.githubusercontent.com/12729184/116673475-07917200-a9d6-11eb-947e-a6f68cce58df.png)

#### 10. 指定单元格开始读取数据

```csharp
MiniExcel.Query(path,useHeaderRow:true,startCell:"B3")
```

![image](https://user-images.githubusercontent.com/12729184/117260316-8593c400-ae81-11eb-9877-c087b7ac2b01.png)

#### 11. 合并的单元格填充

注意 : 效率相对于`没有使用合并填充`来说差    
底层原因 : OpenXml 标准将 mergeCells 放在文件最下方，导致需要遍历两次 sheetxml

```csharp
	var config = new OpenXmlConfiguration()
	{
		FillMergedCells = true
	};
	var rows = MiniExcel.Query(path, configuration: config);
```

![image](https://user-images.githubusercontent.com/12729184/117973630-3527d500-b35f-11eb-95c3-bde255f8114e.png)


支持不固定长宽多行列填充

![image](https://user-images.githubusercontent.com/12729184/117973820-6d2f1800-b35f-11eb-88d8-555063938108.png)





#### 12. 读取大文件硬盘缓存 (Disk-Base Cache - SharedString)

概念 : MiniExcel 当判断文件 SharedString 大小超过 5MB，预设会使用本地缓存，如 [10x100000.xlsx](https://github.com/MiniExcel/MiniExcel/files/8403819/NotDuplicateSharedStrings_10x100000.xlsx)(一百万笔数据)，读取不开启本地缓存需要最高内存使用约195MB，开启后降为65MB。但要特别注意，此优化是以`时间换取内存减少`，所以读取效率会变慢，此例子读取时间从 7.4 秒提高到 27.2 秒，假如不需要能用以下代码关闭硬盘缓存

```csharp
var config = new OpenXmlConfiguration { EnableSharedStringCache = false };
MiniExcel.Query(path,configuration: config)
```

也能使用 SharedStringCacheSize 调整 sharedString 文件大小超过指定大小才做硬盘缓存
```csharp
var config = new OpenXmlConfiguration { SharedStringCacheSize=500*1024*1024 };
MiniExcel.Query(path, configuration: config);
```


![image](https://user-images.githubusercontent.com/12729184/161411851-1c3f72a7-33b3-4944-84dc-ffc1d16747dd.png)

![image](https://user-images.githubusercontent.com/12729184/161411825-17f53ec7-bef4-4b16-b234-e24799ea41b0.png)





### 写/导出 Excel  <a name="getstart2"></a>

1. 必须是非abstract 类别有公开无参数构造函数
2. MiniExcel SaveAs 支援 `IEnumerable参数延迟查询`，除非必要请不要使用 ToList 等方法读取全部数据到内存

图片 : 是否呼叫 ToList 的内存差别  

#### ![image](https://user-images.githubusercontent.com/12729184/112587389-752b0b00-8e38-11eb-8a52-cfb76c57e5eb.png)1. 支持集合<匿名类别>或是<强型别> [[Try it]](https://dotnetfiddle.net/w5WD1J)

```csharp
var path = Path.Combine(Path.GetTempPath(), $"{Guid.NewGuid()}.xlsx");
MiniExcel.SaveAs(path, new[] {
    new { Column1 = "MiniExcel", Column2 = 1 },
    new { Column1 = "Github", Column2 = 2}
});
```



#### 2. `IEnumerable<IDictionary<string, object>>`

```csharp
var values = new List<Dictionary<string, object>>()
{
    new Dictionary<string,object>{{ "Column1", "MiniExcel" }, { "Column2", 1 } },
    new Dictionary<string,object>{{ "Column1", "Github" }, { "Column2", 2 } }
};
MiniExcel.SaveAs(path, values);
```

output : 

| Column1   | Column2 |
| --------- | ------- |
| MiniExcel | 1       |
| Github    | 2       |



#### 3.  IDataReader 

- 推荐使用，可以避免载入全部数据到内存

```csharp
MiniExcel.SaveAs(path, reader);
```

![image](https://user-images.githubusercontent.com/12729184/121275378-149a5e80-c8bc-11eb-85fe-5453552134f0.png)

推荐 DataReader 多表格导出方式(建议使用 Dapper ExecuteReader )

```csharp
using (var cnn = Connection)
{
    cnn.Open();
    var sheets = new Dictionary<string,object>();
    sheets.Add("sheet1", cnn.ExecuteReader("select 1 id"));
    sheets.Add("sheet2", cnn.ExecuteReader("select 2 id"));
    MiniExcel.SaveAs("Demo.xlsx", sheets);
}
```



####  4. Datatable

- 不推荐使用，会将数据全载入内存
- 优先使用 Caption 当栏位名称

```csharp
var path = Path.Combine(Path.GetTempPath(), $"{Guid.NewGuid()}.xlsx");
var table = new DataTable();
{
    table.Columns.Add("Column1", typeof(string));
    table.Columns.Add("Column2", typeof(decimal));
    table.Rows.Add("MiniExcel", 1);
    table.Rows.Add("Github", 2);
}

MiniExcel.SaveAs(path, table);
```

####  5. Dapper Query

- `不推荐使用`，会将数据全载入内存，建议使用`ExecuteReader`

```csharp
using (var connection = GetConnection(connectionString))
{
    var rows = connection.Query(@"select 'MiniExcel' as Column1,1 as Column2 union all select 'Github',2");
    MiniExcel.SaveAs(path, rows);
}
```



#### 6. SaveAs 支持 Stream，生成文件不落地 [[Try it]](https://dotnetfiddle.net/JOen0e)

```csharp
using (var stream = new MemoryStream()) //支持 FileStream,MemoryStream..等
{
    stream.SaveAs(values);
}
```

像是 API 导出 Excel

```csharp
public IActionResult DownloadExcel()
{
    var values = new[] {
        new { Column1 = "MiniExcel", Column2 = 1 },
        new { Column1 = "Github", Column2 = 2}
    };

    var memoryStream = new MemoryStream();
    memoryStream.SaveAs(values);
    memoryStream.Seek(0, SeekOrigin.Begin);
    return new FileStreamResult(memoryStream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
    {
        FileDownloadName = "demo.xlsx"
    };
}
```



#### 7. 创建多个工作表(Sheet)

```csharp
// 1. Dictionary<string,object>
var users = new[] { new { Name = "Jack", Age = 25 }, new { Name = "Mike", Age = 44 } };
var department = new[] { new { ID = "01", Name = "HR" }, new { ID = "02", Name = "IT" } };
var sheets = new Dictionary<string, object>
{
    ["users"] = users,
    ["department"] = department
};
MiniExcel.SaveAs(path, sheets);

// 2. DataSet
var sheets = new DataSet();
sheets.Add(UsersDataTable);
sheets.Add(DepartmentDataTable);
//..
MiniExcel.SaveAs(path, sheets);
```

![image](https://user-images.githubusercontent.com/12729184/118130875-6e7c4580-b430-11eb-9b82-22f02716bd63.png)

#### 8. 表格样式选择

预设样式为

![image](https://user-images.githubusercontent.com/12729184/138234373-cfa97109-b71f-4711-b7f5-0eaaa4a0a3a6.png)

不需要样式

```csharp
var config = new OpenXmlConfiguration()
{
    TableStyles = TableStyles.None
};
MiniExcel.SaveAs(path, value,configuration:config);
```

![image](https://user-images.githubusercontent.com/12729184/118784917-f3e57700-b8c2-11eb-8718-8d955b1bc197.png)

#### 9. AutoFilter 筛选

从 0.19.0 支持，可藉由 OpenXmlConfiguration.AutoFilter 设定，预设为True。关闭 AutoFilter 方式 :  

```csharp
MiniExcel.SaveAs(path, value, configuration: new OpenXmlConfiguration() { AutoFilter = false });
```



#### 10. 图片生成

注意 : 目前此功能不支持避免OOM

```csharp
var value = new[] {
    new { Name="github",Image=File.ReadAllBytes(PathHelper.GetFile("images/github_logo.png"))},
    new { Name="google",Image=File.ReadAllBytes(PathHelper.GetFile("images/google_logo.png"))},
    new { Name="microsoft",Image=File.ReadAllBytes(PathHelper.GetFile("images/microsoft_logo.png"))},
    new { Name="reddit",Image=File.ReadAllBytes(PathHelper.GetFile("images/reddit_logo.png"))},
    new { Name="statck_overflow",Image=File.ReadAllBytes(PathHelper.GetFile("images/statck_overflow_logo.png"))},
};
MiniExcel.SaveAs(path, value);
```

![image](https://user-images.githubusercontent.com/12729184/150462383-ad9931b3-ed8d-4221-a1d6-66f799743433.png)



#### 11. Byte Array 文件导出

从 1.22.0 开始，当值类型为 `byte[]` 系统预设会转成保存文件路径以便导入时转回 `byte[]`，如不想转换可以将 `OpenXmlConfiguration.EnableConvertByteArray` 改为 `false`，能提升系统效率。

![image](https://user-images.githubusercontent.com/12729184/153702334-c3b834f4-6ae4-4ddf-bd4e-e5005d5d8c6a.png)








### 模板填充 Excel <a name="getstart3"></a>

- 宣告方式类似 Vue 模板 `{{变量名称}}`, 或是集合渲染 `{{集合名称.栏位名称}}`
- 集合渲染支持 IEnumerable/DataTable/DapperRow

#### 1. 基本填充

模板:  
![image](https://user-images.githubusercontent.com/12729184/114537556-ed8d2b00-9c84-11eb-8303-a69f62c41e5b.png)

最终效果:  
![image](https://user-images.githubusercontent.com/12729184/114537490-d8180100-9c84-11eb-8c69-db58692f3a85.png)

代码:  
```csharp
// 1. By POCO
var value = new
{
    Name = "Jack",
    CreateDate = new DateTime(2021, 01, 01),
    VIP = true,
    Points = 123
};
MiniExcel.SaveAsByTemplate(path, templatePath, value);


// 2. By Dictionary
var value = new Dictionary<string, object>()
{
    ["Name"] = "Jack",
    ["CreateDate"] = new DateTime(2021, 01, 01),
    ["VIP"] = true,
    ["Points"] = 123
};
MiniExcel.SaveAsByTemplate(path, templatePath, value);
```



#### 2. IEnumerable 数据填充

> Note1: 同行从左往右以第一个 IEnumerableUse 当列表来源 (不支持同列多集合)

模板:   
![image](https://user-images.githubusercontent.com/12729184/114564652-14f2f080-9ca3-11eb-831f-09e3fedbc5fc.png)

最终效果:   
![image](https://user-images.githubusercontent.com/12729184/114564204-b2015980-9ca2-11eb-900d-e21249f93f7c.png)

代码:   

```csharp
//1. By POCO
var value = new
{
    employees = new[] {
        new {name="Jack",department="HR"},
        new {name="Lisa",department="HR"},
        new {name="John",department="HR"},
        new {name="Mike",department="IT"},
        new {name="Neo",department="IT"},
        new {name="Loan",department="IT"}
    }
};
MiniExcel.SaveAsByTemplate(path, templatePath, value);

//2. By Dictionary
var value = new Dictionary<string, object>()
{
    ["employees"] = new[] {
        new {name="Jack",department="HR"},
        new {name="Lisa",department="HR"},
        new {name="John",department="HR"},
        new {name="Mike",department="IT"},
        new {name="Neo",department="IT"},
        new {name="Loan",department="IT"}
    }
};
MiniExcel.SaveAsByTemplate(path, templatePath, value);
```



#### 3. 复杂数据填充

> Note: 支持多 sheet 填充,并共用同一组参数

模板:     

![image](https://user-images.githubusercontent.com/12729184/114565255-acf0da00-9ca3-11eb-8a7f-8131b2265ae8.png)

最终效果:     

![image](https://user-images.githubusercontent.com/12729184/114565329-bf6b1380-9ca3-11eb-85e3-3969e8bf6378.png)

代码:     

```csharp
// 1. By POCO
var value = new
{
    title = "FooCompany",
    managers = new[] {
        new {name="Jack",department="HR"},
        new {name="Loan",department="IT"}
    },
    employees = new[] {
        new {name="Wade",department="HR"},
        new {name="Felix",department="HR"},
        new {name="Eric",department="IT"},
        new {name="Keaton",department="IT"}
    }
};
MiniExcel.SaveAsByTemplate(path, templatePath, value);

// 2. By Dictionary
var value = new Dictionary<string, object>()
{
    ["title"] = "FooCompany",
    ["managers"] = new[] {
        new {name="Jack",department="HR"},
        new {name="Loan",department="IT"}
    },
    ["employees"] = new[] {
        new {name="Wade",department="HR"},
        new {name="Felix",department="HR"},
        new {name="Eric",department="IT"},
        new {name="Keaton",department="IT"}
    }
};
MiniExcel.SaveAsByTemplate(path, templatePath, value);
```

#### 4. 大数据填充效率比较

> NOTE: 在 MiniExcel 使用 IEnumerable 延迟 ( 不ToList ) 可以节省内存使用

![image](https://user-images.githubusercontent.com/12729184/114577091-5046ec80-9cae-11eb-924b-087c7becf8da.png)

#### 5. Cell 值自动类别对应

模板   

![image](https://user-images.githubusercontent.com/12729184/114802504-64830a80-9dd0-11eb-8d56-8e8c401b3ace.png)

最终效果   

![image](https://user-images.githubusercontent.com/12729184/114802419-43221e80-9dd0-11eb-9ffe-a2ce34fe7076.png)

类别   

```csharp
public class Poco
{
    public string @string { get; set; }
    public int? @int { get; set; }
    public decimal? @decimal { get; set; }
    public double? @double { get; set; }
    public DateTime? datetime { get; set; }
    public bool? @bool { get; set; }
    public Guid? Guid { get; set; }
}
```

代码

```csharp
var poco = new TestIEnumerableTypePoco { @string = "string", @int = 123, @decimal = decimal.Parse("123.45"), @double = (double)123.33, @datetime = new DateTime(2021, 4, 1), @bool = true, @Guid = Guid.NewGuid() };
var value = new
{
    Ts = new[] {
        poco,
        new TestIEnumerableTypePoco{},
        null,
        poco
    }
};
MiniExcel.SaveAsByTemplate(path, templatePath, value);
```



#### 6. Example :  列出 Github 专案

模板    

![image](https://user-images.githubusercontent.com/12729184/115068623-12073280-9f25-11eb-9124-f4b3efcdb2a7.png)


最终效果    

![image](https://user-images.githubusercontent.com/12729184/115068639-1a5f6d80-9f25-11eb-9f45-27c434d19a78.png)

代码    

```csharp
var projects = new[]
{
    new {Name = "MiniExcel",Link="https://github.com/shps951023/MiniExcel",Star=146, CreateTime=new DateTime(2021,03,01)},
    new {Name = "HtmlTableHelper",Link="https://github.com/shps951023/HtmlTableHelper",Star=16, CreateTime=new DateTime(2020,02,01)},
    new {Name = "PocoClassGenerator",Link="https://github.com/shps951023/PocoClassGenerator",Star=16, CreateTime=new DateTime(2019,03,17)}
};
var value = new
{
    User = "ITWeiHan",
    Projects = projects,
    TotalStar = projects.Sum(s => s.Star)
};
MiniExcel.SaveAsByTemplate(path, templatePath, value);
```



#### 7. DataTable 当参数

```csharp
var managers = new DataTable();
{
    managers.Columns.Add("name");
    managers.Columns.Add("department");
    managers.Rows.Add("Jack", "HR");
    managers.Rows.Add("Loan", "IT");
}
var value = new Dictionary<string, object>()
{
    ["title"] = "FooCompany",
    ["managers"] = managers,
};
MiniExcel.SaveAsByTemplate(path, templatePath, value);
```

#### 8. 其他

##### 1. 检查模版参数

从 V1.24.0 版本开始，预设忽略模版不存在的参数Key，IgnoreTemplateParameterMissing 可以决定是否抛出错误

```csharp
var config = new OpenXmlConfiguration()
{
    IgnoreTemplateParameterMissing = false,
};
MiniExcel.SaveAsByTemplate(path, templatePath, value, config)
```

![image](https://user-images.githubusercontent.com/12729184/157464332-e316f829-54aa-4c84-a5aa-9aef337b668d.png)





### Excel 列属性 (Excel Column Attribute) <a name="getstart4"></a>



#### 1. 指定列名称、指定第几列、是否忽略该列

Excel例子

![image](https://user-images.githubusercontent.com/12729184/114230869-3e163700-99ac-11eb-9a90-2039d4b4b313.png)


代码
```csharp
public class ExcelAttributeDemo
{
    [ExcelColumnName("Column1")]
    public string Test1 { get; set; }
    [ExcelColumnName("Column2")]
    public string Test2 { get; set; }
    [ExcelIgnore]
    public string Test3 { get; set; }
    [ExcelColumnIndex("I")] // 系统会自动转换"I"为第8列
    public string Test4 { get; set; } 
    public string Test5 { get; } //系统会忽略此列
    public string Test6 { get; private set; } //set非公开,系统会忽略
    [ExcelColumnIndex(3)] // 从0开始索引
    public string Test7 { get; set; }
}

var rows = MiniExcel.Query<ExcelAttributeDemo>(path).ToList();
Assert.Equal("Column1", rows[0].Test1);
Assert.Equal("Column2", rows[0].Test2);
Assert.Null(rows[0].Test3);
Assert.Equal("Test7", rows[0].Test4);
Assert.Null(rows[0].Test5);
Assert.Null(rows[0].Test6);
Assert.Equal("Test4", rows[0].Test7);
```

#### 2. 自定义Format格式 (ExcelFormatAttribute)

從 V0.21.0 開始支持有 `ToString(string content)` 的類別 format

类别

```csharp
public class Dto
{
    public string Name { get; set; }

    [ExcelFormat("MMMM dd, yyyy")]
    public DateTime InDate { get; set; }
}
```

代码

```csharp
var value = new Dto[] {
    new Issue241Dto{ Name="Jack",InDate=new DateTime(2021,01,04)},
    new Issue241Dto{ Name="Henry",InDate=new DateTime(2020,04,05)},
};
MiniExcel.SaveAs(path, value);
```

效果

![image](https://user-images.githubusercontent.com/12729184/118910788-ab2bcd80-b957-11eb-8d42-bfce36621b1b.png)

Query 支持自定义格式转换

![image](https://user-images.githubusercontent.com/12729184/118911286-87b55280-b958-11eb-9a88-c8ff403d240a.png)

#### 3. 指定列宽(ExcelColumnWidthAttribute)

```csharp
public class Dto
{
    [ExcelColumnWidth(20)]
    public int ID { get; set; }
    [ExcelColumnWidth(15.50)]
    public string Name { get; set; }
}
```

#### 4. 多列名对应同一属性

```csharp
public class Dto
{
    [ExcelColumnName(excelColumnName:"EmployeeNo",aliases:new[] { "EmpNo","No" })]
    public string Empno { get; set; }
    public string Name { get; set; }
}
```



#### 5. System.ComponentModel.DisplayNameAttribute = ExcelColumnName.excelColumnNameAttribute

从 1.24.0 开始支持 System.ComponentModel.DisplayNameAttribute 等同于 ExcelColumnName.excelColumnNameAttribute 效果

```C#
public class TestIssueI4TXGTDto
{
    public int ID { get; set; }
    public string Name { get; set; }
    [DisplayName("Specification")]
    public string Spc { get; set; }
    [DisplayName("Unit Price")]
    public decimal Up { get; set; }
}
```

#### 6. ExcelColumnAttribute 

从 1.26.0 版本开始，可以简化多Attribute写法
```csharp
        public class TestIssueI4ZYUUDto
        {
            [ExcelColumn(Name = "ID",Index =0)]
            public string MyProperty { get; set; }
            [ExcelColumn(Name = "CreateDate", Index = 1,Format ="yyyy-MM",Width =100)]
            public DateTime MyProperty2 { get; set; }
        }
```

#### 7. DynamicColumnAttribute 动态设定 Column 

从 1.26.0 版本开始，可以动态设定 Column 的属性
```csharp
            var config = new OpenXmlConfiguration
            {
                DynamicColumns = new DynamicExcelColumn[] { 
                    new DynamicExcelColumn("id"){Ignore=true},
                    new DynamicExcelColumn("name"){Index=1,Width=10},
                    new DynamicExcelColumn("createdate"){Index=0,Format="yyyy-MM-dd",Width=15},
                    new DynamicExcelColumn("point"){Index=2,Name="Account Point"},
                }
            };
            var path = PathHelper.GetTempPath();
            var value = new[] { new { id = 1, name = "Jack", createdate = new DateTime(2022, 04, 12) ,point = 123.456} };
            MiniExcel.SaveAs(path, value, configuration: config);
```
![image](https://user-images.githubusercontent.com/12729184/164510353-5aecbc4e-c3ce-41e8-b6cf-afd55eb23b68.png)



### 新增、删除、修改

#### 新增

v1.28.0 开始支持 CSV 插入新增，在最后一行新增N笔数据

```csharp
// 原始数据
{
    var value = new[] {
          new { ID=1,Name ="Jack",InDate=new DateTime(2021,01,03)},
          new { ID=2,Name ="Henry",InDate=new DateTime(2020,05,03)},
    };
    MiniExcel.SaveAs(path, value);
}
// 最后一行新增一行数据
{ 
    var value = new { ID=3,Name = "Mike", InDate = new DateTime(2021, 04, 23) };
    MiniExcel.Insert(path, value);
}
// 最后一行新增N行数据
{
    var value = new[] {
          new { ID=4,Name ="Frank",InDate=new DateTime(2021,06,07)},
          new { ID=5,Name ="Gloria",InDate=new DateTime(2022,05,03)},
    };
    MiniExcel.Insert(path, value);
}
```

![image](https://user-images.githubusercontent.com/12729184/191023733-1e2fa732-db5c-4a3a-9722-b891fe5aa069.png)



#### 删除(未完成)

#### 修改(未完成)

### Excel 类别自动判断 <a name="getstart5"></a>

- MiniExcel 预设会根据`文件扩展名`判断是 xlsx 还是 csv，但会有失准时候，请自行指定。
- Stream 类别无法判断来源于哪种 excel 请自行指定

```csharp
stream.SaveAs(excelType:ExcelType.CSV);
//or
stream.SaveAs(excelType:ExcelType.XLSX);
//or
stream.Query(excelType:ExcelType.CSV);
//or
stream.Query(excelType:ExcelType.XLSX);
```



### CSV

#### 概念

- 预设全以字串类型返回，预设不会转换为数字或者日期，除非有强型别定义泛型



#### 自定分隔符

预设以 `,` 作为分隔符，自定义请修改 `Seperator` 属性

```csharp
var config = new MiniExcelLibs.Csv.CsvConfiguration() 
{
    Seperator=';'
};
MiniExcel.SaveAs(path, values,configuration: config);
```



#### 自定义换行符

预设以 `\r\n` 作为换行符，自定义请修改 `NewLine` 属性

```csharp
var config = new MiniExcelLibs.Csv.CsvConfiguration() 
{
    NewLine='\n'
};
MiniExcel.SaveAs(path, values,configuration: config);
```



#### 自定义编码

- 预设编码为「从Byte顺序标记检测编码」(detectEncodingFromByteOrderMarks: true)
- 有自定义编码需求，请修改 StreamReaderFunc /  StreamWriterFunc 属性

```csharp
// Read
var config = new MiniExcelLibs.Csv.CsvConfiguration()
{
    StreamReaderFunc = (stream) => new StreamReader(stream,Encoding.GetEncoding("gb2312"))
};
var rows = MiniExcel.Query(path, true,excelType:ExcelType.CSV,configuration: config);

// Write
var config = new MiniExcelLibs.Csv.CsvConfiguration()
{
    StreamWriterFunc = (stream) => new StreamWriter(stream, Encoding.GetEncoding("gb2312"))
};
MiniExcel.SaveAs(path, value,excelType:ExcelType.CSV, configuration: config);
```



### DataReader

#### 1. GetReader

从 1.23.0 版本开始能获取 DataReader

```csharp
    using (var reader = MiniExcel.GetReader(path,true))
    {
        while (reader.Read())
        {
            for (int i = 0; i < reader.FieldCount; i++)
            {
                var value = reader.GetValue(i);
            }
        }
    }
```





### 异步 Async

- 从 v0.17.0 版本开始支持异步 (感谢[isdaniel ( SHIH,BING-SIOU)](https://github.com/isdaniel))

```csharp
public static Task SaveAsAsync(string path, object value, bool printHeader = true, string sheetName = "Sheet1", ExcelType excelType = ExcelType.UNKNOWN, IConfiguration configuration = null)
public static Task SaveAsAsync(this Stream stream, object value, bool printHeader = true, string sheetName = "Sheet1", ExcelType excelType = ExcelType.XLSX, IConfiguration configuration = null)
public static Task<IEnumerable<dynamic>> QueryAsync(string path, bool useHeaderRow = false, string sheetName = null, ExcelType excelType = ExcelType.UNKNOWN, string startCell = "A1", IConfiguration configuration = null)
public static Task<IEnumerable<T>> QueryAsync<T>(this Stream stream, string sheetName = null, ExcelType excelType = ExcelType.UNKNOWN, string startCell = "A1", IConfiguration configuration = null) where T : class, new()    
public static Task<IEnumerable<T>> QueryAsync<T>(string path, string sheetName = null, ExcelType excelType = ExcelType.UNKNOWN, string startCell = "A1", IConfiguration configuration = null) where T : class, new() 
public static Task<IEnumerable<IDictionary<string, object>>> QueryAsync(this Stream stream, bool useHeaderRow = false, string sheetName = null, ExcelType excelType = ExcelType.UNKNOWN, string startCell = "A1", IConfiguration configuration = null)
public static Task SaveAsByTemplateAsync(this Stream stream, string templatePath, object value)
public static Task SaveAsByTemplateAsync(this Stream stream, byte[] templateBytes, object value)    
public static Task SaveAsByTemplateAsync(string path, string templatePath, object value)
public static Task SaveAsByTemplateAsync(string path, byte[] templateBytes, object value) 
public static Task<DataTable> QueryAsDataTableAsync(string path, bool useHeaderRow = true, string sheetName = null, ExcelType excelType = ExcelType.UNKNOWN, string startCell = "A1", IConfiguration configuration = null)
```

- 从 v1.25.0 开始支持 `cancellationToken`。



### 其他

#### 1. 映射枚举(enum)

系统会自动映射(注意:大小写不敏感)

![image](https://user-images.githubusercontent.com/12729184/116210595-9784b100-a775-11eb-936f-8e7a8b435961.png)

从V0.18.0版本开始支持Enum Description

```csharp
public class Dto
{
    public string Name { get; set; }
    public I49RYZUserType UserType { get; set; }
}      

public enum Type
{
    [Description("General User")]
    V1,
    [Description("General Administrator")]
    V2,
    [Description("Super Administrator")]
    V3
}
```

![image](https://user-images.githubusercontent.com/12729184/133116630-27cc7161-099a-48b8-9784-cd1e443af3d1.png)

#### 2. CSV 转 XLSX 或是 XLSX 转 CSV

```csharp
MiniExcel.ConvertXlsxToCsv(xlsxPath, csvPath);
MiniExcel.ConvertXlsxToCsv(xlsxStream, csvStream);
MiniExcel.ConvertXlsxToCsv(csvPath, xlsxPath);
MiniExcel.ConvertXlsxToCsv(csvStream, xlsxStream);
```



#### 3. 自定义 CultureInfo

从 1.22.0 版本开始，可以使用以下代码自定义文化信息，系统预设 `CultureInfo.InvariantCulture`。

```csharp
var config = new CsvConfiguration()
{
	Culture = new CultureInfo("fr-FR"),
};
MiniExcel.SaveAs(path, value, configuration: config);

//or
MiniExcel.Query(path, configuration: config);
```

#### 4. 导出自定义 Buffer Size
```csharp
    public abstract class Configuration : IConfiguration
    {
        public int BufferSize { get; set; } = 1024 * 512;
    }
```



### 例子

#### 1. SQLite & Dapper 读取大数据新增到数据库

Note : 请不要呼叫 call ToList/ToArray 等方法，这会将所有数据读到内存内

```csharp
using (var connection = new SQLiteConnection(connectionString))
{
    connection.Open();
    using (var transaction = connection.BeginTransaction())
    using (var stream = File.OpenRead(path))
    {
       var rows = stream.Query();
       foreach (var row in rows)
             connection.Execute("insert into T (A,B) values (@A,@B)", new { row.A, row.B }, transaction: transaction);
       transaction.Commit();
    }
}
```

效能:
![image](https://user-images.githubusercontent.com/12729184/111072579-2dda7b80-8516-11eb-9843-c01a1edc88ec.png)


#### 2. ASP.NET Core 3.1 下载/上传 Excel Xlsx API Demo [Try it](tests/MiniExcel.Tests.AspNetCore)

```csharp
public class ApiController : Controller
{
    public IActionResult Index()
    {
        return new ContentResult
        {
            ContentType = "text/html",
            StatusCode = (int)HttpStatusCode.OK,
            Content = @"<html><body>
<a href='api/DownloadExcel'>DownloadExcel</a><br>
<a href='api/DownloadExcelFromTemplatePath'>DownloadExcelFromTemplatePath</a><br>
<a href='api/DownloadExcelFromTemplateBytes'>DownloadExcelFromTemplateBytes</a><br>
<p>Upload Excel</p>
<form method='post' enctype='multipart/form-data' action='/api/uploadexcel'>
    <input type='file' name='excel'> <br>
    <input type='submit' >
</form>
</body></html>"
        };
    }

    public IActionResult DownloadExcel()
    {
        var values = new[] {
            new { Column1 = "MiniExcel", Column2 = 1 },
            new { Column1 = "Github", Column2 = 2}
        };
        var memoryStream = new MemoryStream();
        memoryStream.SaveAs(values);
        memoryStream.Seek(0, SeekOrigin.Begin);
        return new FileStreamResult(memoryStream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
        {
            FileDownloadName = "demo.xlsx"
        };
    }

    public IActionResult DownloadExcelFromTemplatePath()
    {
        string templatePath = "TestTemplateComplex.xlsx";

        Dictionary<string, object> value = new Dictionary<string, object>()
        {
            ["title"] = "FooCompany",
            ["managers"] = new[] {
                new {name="Jack",department="HR"},
                new {name="Loan",department="IT"}
            },
            ["employees"] = new[] {
                new {name="Wade",department="HR"},
                new {name="Felix",department="HR"},
                new {name="Eric",department="IT"},
                new {name="Keaton",department="IT"}
            }
        };

        MemoryStream memoryStream = new MemoryStream();
        memoryStream.SaveAsByTemplate(templatePath, value);
        memoryStream.Seek(0, SeekOrigin.Begin);
        return new FileStreamResult(memoryStream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
        {
            FileDownloadName = "demo.xlsx"
        };
    }

    private static Dictionary<string, Byte[]> TemplateBytesCache = new Dictionary<string, byte[]>();

    static ApiController()
    {
        string templatePath = "TestTemplateComplex.xlsx";
        byte[] bytes = System.IO.File.ReadAllBytes(templatePath);
        TemplateBytesCache.Add(templatePath, bytes);
    }

    public IActionResult DownloadExcelFromTemplateBytes()
    {
        byte[] bytes = TemplateBytesCache["TestTemplateComplex.xlsx"];

        Dictionary<string, object> value = new Dictionary<string, object>()
        {
            ["title"] = "FooCompany",
            ["managers"] = new[] {
                new {name="Jack",department="HR"},
                new {name="Loan",department="IT"}
            },
            ["employees"] = new[] {
                new {name="Wade",department="HR"},
                new {name="Felix",department="HR"},
                new {name="Eric",department="IT"},
                new {name="Keaton",department="IT"}
            }
        };

        MemoryStream memoryStream = new MemoryStream();
        memoryStream.SaveAsByTemplate(bytes, value);
        memoryStream.Seek(0, SeekOrigin.Begin);
        return new FileStreamResult(memoryStream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet")
        {
            FileDownloadName = "demo.xlsx"
        };
    }

    public IActionResult UploadExcel(IFormFile excel)
    {
        var stream = new MemoryStream();
        excel.CopyTo(stream);

        foreach (var item in stream.Query(true))
        {
            // do your logic etc.
        }

        return Ok("File uploaded successfully");
    }
}
```

####  3. 分页查询

```csharp
void Main()
{
	var rows = MiniExcel.Query(path);
	
	Console.WriteLine("==== No.1 Page ====");
	Console.WriteLine(Page(rows,pageSize:3,page:1));
	Console.WriteLine("==== No.50 Page ====");
	Console.WriteLine(Page(rows,pageSize:3,page:50));
	Console.WriteLine("==== No.5000 Page ====");
	Console.WriteLine(Page(rows,pageSize:3,page:5000));
}

public static IEnumerable<T> Page<T>(IEnumerable<T> en, int pageSize, int page)
{
	return en.Skip(page * pageSize).Take(pageSize);
}
```

![20210419](https://user-images.githubusercontent.com/12729184/114679083-6ef4c400-9d3e-11eb-9f78-a86daa45fe46.gif)

#### 4. WebForm不落地导出Excel

```csharp
var fileName = "Demo.xlsx";
var sheetName = "Sheet1";
HttpResponse response = HttpContext.Current.Response;
response.Clear();
response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
response.AddHeader("Content-Disposition", $"attachment;filename=\"{fileName}\"");
var values = new[] {
    new { Column1 = "MiniExcel", Column2 = 1 },
    new { Column1 = "Github", Column2 = 2}
};
var memoryStream = new MemoryStream();
memoryStream.SaveAs(values, sheetName: sheetName);
memoryStream.Seek(0, SeekOrigin.Begin);
memoryStream.CopyTo(Response.OutputStream);
response.End();
```



#### 5. 动态 i18n 多国语言跟权限管理

像例子一样，建立一个方法处理 i18n 跟权限管理，并搭配 `yield return 返回 IEnumerable<Dictionary<string, object>>`，即可达到动态、低内存处理效果

```csharp
void Main()
{
	var value = new Order[] {
		new Order(){OrderNo = "SO01",CustomerID="C001",ProductID="P001",Qty=100,Amt=500},
		new Order(){OrderNo = "SO02",CustomerID="C002",ProductID="P002",Qty=300,Amt=400},
	};

	Console.WriteLine("en-Us and Sales role");
	{
		var path = Path.GetTempPath() + Guid.NewGuid() + ".xlsx";
		var lang = "en-US";
		var role = "Sales";
		MiniExcel.SaveAs(path, GetOrders(lang, role, value));
		MiniExcel.Query(path, true).Dump();
	}

	Console.WriteLine("zh-CN and PMC role");
	{
		var path = Path.GetTempPath() + Guid.NewGuid() + ".xlsx";
		var lang = "zh-CN";
		var role = "PMC";
		MiniExcel.SaveAs(path, GetOrders(lang, role, value));
		MiniExcel.Query(path, true).Dump();
	}
}

private IEnumerable<Dictionary<string, object>> GetOrders(string lang, string role, Order[] orders)
{
	foreach (var order in orders)
	{
		var newOrder = new Dictionary<string, object>();

		if (lang == "zh-CN")
		{
			newOrder.Add("客户编号", order.CustomerID);
			newOrder.Add("订单编号", order.OrderNo);
			newOrder.Add("产品编号", order.ProductID);
			newOrder.Add("数量", order.Qty);
			if (role == "Sales")
				newOrder.Add("价格", order.Amt);
			yield return newOrder;
		}
		else if (lang == "en-US")
		{
			newOrder.Add("Customer ID", order.CustomerID);
			newOrder.Add("Order No", order.OrderNo);
			newOrder.Add("Product ID", order.ProductID);
			newOrder.Add("Quantity", order.Qty);
			if (role == "Sales")
				newOrder.Add("Amount", order.Amt);
			yield return newOrder;
		}
		else
		{
			throw new InvalidDataException($"lang {lang} wrong");
		}
	}
}

public class Order
{
	public string OrderNo { get; set; }
	public string CustomerID { get; set; }
	public decimal Qty { get; set; }
	public string ProductID { get; set; }
	public decimal Amt { get; set; }
}
```

![image](https://user-images.githubusercontent.com/12729184/118939964-d24bc480-b982-11eb-88dd-f06655f6121a.png)









### FAQ 常见问题

#### Q: Excel 表头标题名称跟 class 属性名称不一致，如何对应?

A. 请使用 ExcelColumnName 作 mapping

![image](https://user-images.githubusercontent.com/12729184/116020475-eac50980-a678-11eb-8804-129e87200e5e.png)

#### Q. 多工作表(sheet)如何导出/查询数据?

A. 使用 `GetSheetNames `方法搭配 Query 的 sheetName 参数



```csharp
var sheets = MiniExcel.GetSheetNames(path);
foreach (var sheet in sheets)
{
    Console.WriteLine($"sheet name : {sheet} ");
    var rows = MiniExcel.Query(path,useHeaderRow:true,sheetName:sheet);
    Console.WriteLine(rows);
}
```

![image](https://user-images.githubusercontent.com/12729184/116199841-2a1f5300-a76a-11eb-90a3-6710561cf6db.png)



#### Q. 是否使用 Count 会载入全部数据到内存

不会，图片测试一百万行*十列数据，简单测试，内存最大使用 < 60MB，花费13.65秒

![image](https://user-images.githubusercontent.com/12729184/117118518-70586000-adc3-11eb-9ce3-2ba76cf8b5e5.png)



#### Q. Query如何使用整数索引取值?

Query 预设索引为字串Key : A,B,C....，想要改为数字索引，请建立以下方法自行转换

```csharp
void Main()
{
	var path = @"D:\git\MiniExcel\samples\xlsx\TestTypeMapping.xlsx";
	var rows = MiniExcel.Query(path,true);
	foreach (var r in ConvertToIntIndexRows(rows))
	{
		Console.Write($"column 0 : {r[0]} ,column 1 : {r[1]}");
		Console.WriteLine();
	}
}

private IEnumerable<Dictionary<int, object>> ConvertToIntIndexRows(IEnumerable<object> rows)
{
	ICollection<string> keys = null;
	var isFirst = true;
	foreach (IDictionary<string,object> r in rows)
	{
		if(isFirst)
		{
			keys = r.Keys;
			isFirst = false;
		}
		
		var dic = new Dictionary<int, object>();
		var index = 0;
		foreach (var key in keys)
			dic[index++] = r[key];
		yield return dic;
	}
}
```

#### Q. 导出时数组为空时生成没有标题空 Excel

因为 MiniExcel 使用类似 JSON.NET 动态从值获取类别机制简化 API 操作，没有数据就无法获取类别。可以查看[ issue #133](https://github.com/shps951023/MiniExcel/issues/133) 了解。

![image](https://user-images.githubusercontent.com/12729184/122639771-546c0c00-d12e-11eb-800c-498db27889ca.png)

> 强型别和 DataTable 会生成表头，但 Dicionary 依旧是空 Excel

#### Q. 如何人为空白行中止遍历?

常发生人为不小心在最后几行留下空白行情况，MiniExcel可以搭配 `LINQ TakeWhile`实现空白行中断遍历。

![image](https://user-images.githubusercontent.com/12729184/130209137-162621c2-f337-4479-9996-beeac65bc4d4.png)



#### Q. 不想要空白行如何去除?



![image](https://user-images.githubusercontent.com/12729184/137873865-7107d8f5-eb59-42db-903a-44e80589f1b2.png)



IEnumerable版本

```csharp
public static IEnumerable<dynamic> QueryWithoutEmptyRow(Stream stream, bool useHeaderRow, string sheetName, ExcelType excelType, string startCell, IConfiguration configuration)
{
	var rows = stream.Query(useHeaderRow,sheetName,excelType,startCell,configuration);
	foreach (IDictionary<string,object> row in rows)
	{
		if(row.Keys.Any(key=>row[key]!=null))
			yield return row;
	}
}
```



DataTable版本

```csharp
public static DataTable QueryAsDataTableWithoutEmptyRow(Stream stream, bool useHeaderRow, string sheetName, ExcelType excelType, string startCell, IConfiguration configuration)
{
	if (sheetName == null && excelType != ExcelType.CSV) /*Issue #279*/
		sheetName = stream.GetSheetNames().First();

	var dt = new DataTable(sheetName);
	var first = true;
	var rows = stream.Query(useHeaderRow,sheetName,excelType,startCell,configuration);
	foreach (IDictionary<string, object> row in rows)
	{
		if (first)
		{

			foreach (var key in row.Keys)
			{
				var column = new DataColumn(key, typeof(object)) { Caption = key };
				dt.Columns.Add(column);
			}

			dt.BeginLoadData();
			first = false;
		}

		var newRow = dt.NewRow();
		var isNull=true;
		foreach (var key in row.Keys)
		{
			var _v = row[key];
			if(_v!=null)
				isNull = false;
			newRow[key] = _v; 
		}
		
		if(!isNull)
			dt.Rows.Add(newRow);
	}

	dt.EndLoadData();
	return dt;
}
```



#### Q. 保存如何取代MiniExcel.SaveAs(path, value)，文件存在系统会报已存在错误?

请改以Stream自行管控Stream行为，如

```C#
	using (var stream = File.Create("Demo.xlsx"))
		MiniExcel.SaveAs(stream,value);
```

从V1.25.0版本开始，支持 overwriteFile 參數，方便調整是否要覆蓋已存在文件

```csharp
	MiniExcel.SaveAs(path, value, overwriteFile: true);
```





### 局限与警告

- 目前不支援 xls (97-2003) 或是加密文件
- xlsm 只支持查询



### 参考

[ExcelDataReader](https://github.com/ExcelDataReader/ExcelDataReader)  / [ClosedXML](https://github.com/ClosedXML/ClosedXML) / [Dapper](https://github.com/DapperLib/Dapper) / [ExcelNumberFormat](https://github.com/andersnm/ExcelNumberFormat)



### 感谢名单

####  [Jetbrains](https://www.jetbrains.com/)

![jetbrains-variant-2](https://user-images.githubusercontent.com/12729184/123997015-8456c180-da02-11eb-829a-aec476fe8e94.png)

感谢提供免费IDE支持此项目 ([License](https://user-images.githubusercontent.com/12729184/123988233-6ab17c00-d9fa-11eb-8739-2a08c6a4a263.png))



### Contributors  

![](https://contrib.rocks/image?repo=shps951023/MiniExcel)