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Introduction

MiniExcel is simple and efficient to avoid OOM's .NET processing Excel tool.

At present, most popular frameworks need to load all the data into the memory to facilitate operation, but it will cause memory consumption problems. MiniExcel tries to use algorithm from a stream to reduce the original 1000 MB occupation to a few MB to avoid OOM(out of memory).

Features

• Low memory consumption, avoid OOM (out of memory) and full GC
• Support real-time operation of each row of data
• Support LINQ deferred execution, it can do low-consumption, fast paging and other complex queries
• Lightweight, does not with any third-party dependencies, DLL is less than 100KB
• Easy Dapper API style

Installation

You can install the package from NuGet

Release Notes

Please Check Release Notes

Discussions / TODO

Please Check Discussions / TODO

Performance

Test1,000,000x10.xlsx as performance test basic file,A total of 10,000,000 "HelloWorld" with a file size of 23 MB

Benchmarks logic can be found in MiniExcel.Benchmarks , and test cli

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

Output from the latest run is :

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  

Method	Max Memory Usage	Mean	Gen 0	Gen 1	Gen 2
'MiniExcel QueryFirst'	0.109 MB	726.4 us	-	-	-
'ExcelDataReader QueryFirst'	15.24 MB	10,664,238.2 us	566000.0000	1000.0000	-
'MiniExcel Query'	17.3 MB	14,179,334.8 us	367000.0000	96000.0000	7000.0000
'ExcelDataReader Query'	17.3 MB	22,565,088.7 us	1210000.0000	2000.0000	-
'Epplus QueryFirst'	1,452 MB	18,198,015.4 us	535000.0000	132000.0000	9000.0000
'Epplus Query'	1,451 MB	23,647,471.1 us	1451000.0000	133000.0000	9000.0000
'OpenXmlSDK Query'	1,412 MB	52,003,270.1 us	978000.0000	353000.0000	11000.0000
'OpenXmlSDK QueryFirst'	1,413 MB	52,348,659.1 us	978000.0000	353000.0000	11000.0000
'ClosedXml QueryFirst'	2,158 MB	66,188,979.6 us	2156000.0000	575000.0000	9000.0000
'ClosedXml Query'	2,184 MB	191,434,126.6 us	2165000.0000	577000.0000	10000.0000

Method	Max Memory Usage	Mean	Gen 0	Gen 1	Gen 2
'MiniExcel Create Xlsx'	15 MB	11,531,819.8 us	1020000.0000	-	-
'Epplus Create Xlsx'	1,204 MB	22,509,717.7 us	1370000.0000	60000.0000	30000.0000
'OpenXmlSdk Create Xlsx'	2,621 MB	42,473,998.9 us	1370000.0000	460000.0000	50000.0000
'ClosedXml Create Xlsx'	7,141 MB	140,939,928.6 us	5520000.0000	1500000.0000	80000.0000

Execute a query and map the results to a strongly typed IEnumerable [Try it]

Recommand to use Stream.Query because of better efficiency.

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>();

Execute a query and map it to a list of dynamic objects without using head [Try it]

• dynamic key is A.B.C.D..

MiniExcel	1
Github	2

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);
}

Execute a query with first header row [Try it]

note : same column name use last right one

Input Excel :

Column1	Column2
MiniExcel	1
Github	2

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);
}

Query Support LINQ Extension First/Take/Skip ...etc

Query First

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);
}

Performance between MiniExcel/ExcelDataReader/ClosedXML/EPPlus

Create Excel file [Try it]

1. Must be a non-abstract type with a public parameterless constructor .

2. MiniExcel support parameter IEnumerable Deferred Execution, If you want to use least memory, please do not call methods such as ToList

e.g : ToList or not memory usage

Anonymous or strongly type:

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

Datatable:

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);

Dapper:

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);
}

IEnumerable<IDictionary<string, object>>

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);

Create File Result :

Column1	Column2
MiniExcel	1
Github	2

SaveAs Stream [Try it]

using (var stream = File.Create(path))
{
    stream.SaveAs(values);
}

Excel Column Name/Ignore Attribute

e.g

input excel :

Test1	Test2	Test3	Test4	Test5	Test6	Column1	Column2
Test1	Test2	Test3	Test4	Test5	Test6	Column1	Column2

public class ExcelAttributeDemo
{
    [ExcelColumnName("Column1")]
    public string Test1 { get; set; }
    [ExcelColumnName("Column2")]
    public string Test2 { get; set; }
    [ExcelIgnore]
    public string Test3 { get; set; }
    public string Test4 { get; set; }
    public string Test5 { get; }
    public string Test6 { get; private 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("Test4", rows[0].Test4);
Assert.Null(rows[0].Test5);
Assert.Null(rows[0].Test6);

SQLite & Dapper Large Size File SQL Insert Avoid OOM

note : please don't call ToList/ToArray methods after Query, it'll load all data into memory

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();
    }
}

performance:

ASP.NET Core 3.1 or MVC 5 Download Excel Xlsx API Demo

public class ExcelController : Controller
{
    public IActionResult Download()
    {
        var values = new[] {
            new { Column1 = "MiniExcel", Column2 = 1 },
            new { Column1 = "Github", Column2 = 2}
        };
        var stream = new MemoryStream();
        stream.SaveAs(values);
        return File(stream,
            "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
            "demo.xlsx");
    }
}

Excel Type Auto Check

Default system will auto check file path or stream is from xlsx or csv, but if you need to specify type, it can use excelType parameter.

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

Dynamic Query cast row to IDictionary<string,object>

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

Limitations and caveats

• Not support xls and encrypted file now

Reference

• ExcelDataReader
• StackExchange/Dapper

Contributors :