ant-design-blazor/components/core/Helpers/EnumHelper.cs

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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
namespace AntDesign
{
public static class EnumHelper<T>
{
private static readonly MethodInfo _enumHasFlag = typeof(Enum).GetMethod(nameof(Enum.HasFlag));
private static readonly Func<T, T, T> _aggregateFunction;
private static readonly Func<T, T, bool> _hasFlagFunction;
private static readonly IEnumerable<T> _valueList;
private static readonly IEnumerable<(T Value, string Label)> _valueLabelList;
private static readonly Type _enumType;
private static readonly bool _isFlags;
public static bool IsFlags => _isFlags;
static EnumHelper()
{
_enumType = THelper.GetUnderlyingType<T>();
_aggregateFunction = BuildAggregateFunction();
_valueList = Enum.GetValues(_enumType).Cast<T>();
_valueLabelList = _valueList.Select(value => (value, GetDisplayName(value)));
_isFlags = _enumType.GetCustomAttribute<FlagsAttribute>() != null;
_hasFlagFunction = BuildHasFlagFunction();
}
// There is no constraint or type check for type parameter T, be sure that T is an enumeration type
public static object Combine(IEnumerable<T> enumValues)
{
if (enumValues?.Any() == true)
{
return enumValues.Aggregate(_aggregateFunction);
}
return default(T);
}
public static IEnumerable<T> Split(object enumValue)
{
if (enumValue == null)
{
return Array.Empty<T>();
}
if (enumValue is string enumString)
{
return _valueList.Where(value => enumString.Split(",").Contains(Enum.GetName(_enumType, value)));
}
return _valueList.Where(value => _hasFlagFunction((T)enumValue, value));
}
public static IEnumerable<T> GetValueList()
{
return _valueList;
}
public static IEnumerable<(T Value, string Label)> GetValueLabelList()
{
return _valueLabelList;
}
public static string GetDisplayName(T enumValue)
{
var enumName = Enum.GetName(_enumType, enumValue);
var fieldInfo = _enumType.GetField(enumName);
return fieldInfo.GetCustomAttribute<DisplayAttribute>(true)?.GetName() ?? enumName;
}
private static Func<T, T, T> BuildAggregateFunction()
{
var type = typeof(T);
var underlyingType = Enum.GetUnderlyingType(_enumType);
var param1 = Expression.Parameter(type);
var param2 = Expression.Parameter(type);
var body = Expression.Convert(
Expression.Or(
Expression.Convert(param1, underlyingType),
Expression.Convert(param2, underlyingType)),
type);
return Expression.Lambda<Func<T, T, T>>(body, param1, param2).Compile();
}
private static Func<T, T, bool> BuildHasFlagFunction()
{
var type = typeof(T);
var param1 = Expression.Parameter(type);
var param2 = Expression.Parameter(type);
if (THelper.IsTypeNullable(type))
{
Expression notNull = Expression.NotEqual(param1, Expression.Constant(null));
var param1Value = Expression.MakeMemberAccess(param1, param1.Type.GetMember(nameof(Nullable<int>.Value))[0]);
var param1ValueHasFlags = Expression.Call(param1Value, _enumHasFlag, Expression.Convert(param2, typeof(Enum)));
var notNullAndParam1ValueHasFlags = Expression.AndAlso(notNull, param1ValueHasFlags);
return Expression.Lambda<Func<T, T, bool>>(notNullAndParam1ValueHasFlags, param1, param2).Compile();
}
else
{
var body = Expression.Call(param1, _enumHasFlag, Expression.Convert(param2, typeof(Enum)));
return Expression.Lambda<Func<T, T, bool>>(body, param1, param2).Compile();
}
}
}
}