有没有办法使用反射来设置结构实例的属性？

发布于 2024-11-14 14:59:45 字数 417 浏览 5 评论 0原文

我正在尝试编写一些在结构上设置属性的代码（重要的是它是结构上的属性）并且失败：

System.Drawing.Rectangle rectangle = new System.Drawing.Rectangle();
PropertyInfo propertyInfo = typeof(System.Drawing.Rectangle).GetProperty("Height");
propertyInfo.SetValue(rectangle, 5, null);

高度值（如调试器报告的）永远不会设置为任何内容 - 它保持默认值值为 0。

我之前对课程进行了大量反思，效果很好。另外，我知道在处理结构时，如果设置字段，则需要使用 FieldInfo.SetValueDirect，但我不知道 PropertyInfo 的等效项。

原文

I'm trying to write some code that sets a property on a struct (important that it's a property on a struct) and it's failing:

System.Drawing.Rectangle rectangle = new System.Drawing.Rectangle();
PropertyInfo propertyInfo = typeof(System.Drawing.Rectangle).GetProperty("Height");
propertyInfo.SetValue(rectangle, 5, null);

The Height value (as reported by the debugger) never gets set to anything - it stays at the default value of 0.

I have done plenty of reflection on classes before and this has worked fine. Also, I know that when dealing with structs, you need to use FieldInfo.SetValueDirect if setting a field, but I don't know of an equivalent for PropertyInfo.

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断肠人 2024-11-21 14:59:45

rectangle 的值正在被装箱 - 但随后您将丢失装箱的值，这就是正在修改的值。试试这个：

Rectangle rectangle = new Rectangle();
PropertyInfo propertyInfo = typeof(Rectangle).GetProperty("Height");
object boxed = rectangle;
propertyInfo.SetValue(boxed, 5, null);
rectangle = (Rectangle) boxed;

The value of rectangle is being boxed - but then you're losing the boxed value, which is what's being modified. Try this:

Rectangle rectangle = new Rectangle();
PropertyInfo propertyInfo = typeof(Rectangle).GetProperty("Height");
object boxed = rectangle;
propertyInfo.SetValue(boxed, 5, null);
rectangle = (Rectangle) boxed;

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做个少女永远怀春 2024-11-21 14:59:45

听说过 SetValueDirect？他们成功是有原因的。 :)

struct MyStruct { public int Field; }

static class Program
{
    static void Main()
    {
        var s = new MyStruct();
        s.GetType().GetField("Field").SetValueDirect(__makeref(s), 5);
        System.Console.WriteLine(s.Field); //Prints 5
    }
}

除了未记录的 __makeref 之外，您还可以使用其他方法（请参阅 System.TypedReference），但它们更加痛苦。

Ever heard of SetValueDirect? There's a reason they made it. :)

struct MyStruct { public int Field; }

static class Program
{
    static void Main()
    {
        var s = new MyStruct();
        s.GetType().GetField("Field").SetValueDirect(__makeref(s), 5);
        System.Console.WriteLine(s.Field); //Prints 5
    }
}

There's other methods than the undocumented __makeref which you could use (see System.TypedReference) but they're more painful.

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