Is there a way to set properties on struct instances using reflection?

Question

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.

Answer 1

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; 

Answer 2

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.