c# - 如何使用 PropertyInfo.SetValue Method (Object, Object) 设置可空属性的值

Question

这个问题在这里已经有了答案:





Convert.ChangeType() fails on Nullable Types

(7 个回答)


8 年前关闭。




这是我的代码。它抛出异常“类型'MyEnum.CommonCoreStandard'的对象无法转换为类型'System.Nullable`1[System.Byte]'。”同时设置第二个属性“Prop2”的值。我使用反射的概念将一种类型“BlEntity”转换为另一种类型“UiEntity”

public class BlEntity
{
    //CommonCoreStandard is an enum
    public CommonCoreStandard Prop1 { get; set; }
    public CommonCoreStandard? Prop2 { get; set; }
}

public class UiEntity
{
    public byte Prop1 { get; set; }
    public byte? Prop2 { get; set; }
}

 public void ConvertBlToUi()
    {
        var source = new BlEntity(CommonCoreStandard.KeyIdeasAndDetails, CommonCoreStandard.IntegrationOfKnowledge);
        var target = new UiEntity();

        TypeConverter.ConvertBlToUi(source,target);
 }

    public static void ConvertBlToUi<TBl, TUi>(TBl entitySource, TUi entityTarget)
    {
        var blProperties = typeof(TBl).GetProperties().Select(p => new { Name = p.Name.ToLower(), Property = p }).ToArray();

        var uiProperties = typeof(TUi).GetProperties().Select(p => new { Name = p.Name.ToLower(), Property = p });

        foreach (var uiProperty in uiProperties)
        {
            var value = blProperty.Property.GetValue(entitySource);
            uiProperty.Property.SetValue(entityTarget, value);
        }

    }

Answer 1

    public static void ConvertBlToUi<TBl, TUi>(TBl entitySource, TUi entityTarget)
    {
        var blProperties = typeof(TBl).GetProperties().Select(p => new { Name = p.Name.ToLower(), Property = p }).ToArray();

        var uiProperties = typeof(TUi).GetProperties().Select(p => new { Name = p.Name.ToLower(), Property = p });

        foreach (var uiProperty in uiProperties)
        {
            var value = blProperty.Property.GetValue(entitySource);
            var t = Nullable.GetUnderlyingType(uiProperty.Property.PropertyType) ?? uiProperty.Property.PropertyType;
            var safeValue = (value == null) ? null : Convert.ChangeType(value, t);
            uiProperty.Property.SetValue(entityTarget, safeValue);
        }
    }