反射执行枚举 HasFlag 报错
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悬赏园豆：10
[已解决问题]
解决于 2021-10-06 15:47
/// <summary> /// HasFlag /// </summary> /// <typeparam name="TSource">数据类型</typeparam> /// <param name="pe">左侧表达式参数</param> /// <param name="property">属性</param> /// <param name="value">值</param> /// <returns>表达式</returns> public static Expression HasFlag<TSource>(ParameterExpression pe, string property, object value) { MemberExpression member = pe.GetMemberExpression(property); if (Nullable.GetUnderlyingType(member.Type) != null && value != null) { member = Expression.Property(member, "Value"); } CheckPropertyValueMismatch(member, Expression.Constant(value)); var memberType = member.Member.MemberType == MemberTypes.Property ? (member.Member as PropertyInfo).PropertyType : (member.Member as FieldInfo).FieldType; var isNullType = IsNullableType(memberType); if ((isNullType && memberType?.GetGenericArguments()[0]?.IsEnum == true) || memberType.IsEnum) if (value?.ToString().Contains(",") ?? false) return Expression.Call(member, typeof(Enum).GetMethod("HasFlag",new Type[]{typeof(Enum)}), Expression.Constant(value)); else return Expression.Equal(member, Expression.Constant(value)); else return null; }
表达式明明是支持位移枚举的HasFlag方法的，类似于list.AsQueryable().Where(m=>m.Gender.HasFlag(input.Gender)).ToList()，不懂为啥这里程序报不支持 ， 具体错误如下：
Expression of type 'System.Linq.Expressions.Tests.EnumGender' cannot be used for parameter of type 'System.Enum' of method 'Boolean HasFlag(System.Enum)' (Parameter 'arg0')
最佳答案
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return Expression.Call(member, typeof(Enum).GetMethod("HasFlag", new[] { typeof(Enum) }), Expression.Constant(value, typeof(Enum)));
值要指定一下类型