Adding an Attribute for property in runtime (for design-time purposes)

Question

Hi all,

I need to add an attribute to some property in runtime (for design-time purposes). I know I can do this for classes:

TypeDescriptor.AddAttributes(typeof(MyType), new MyRuntimeAttribute());

But I can't find any way to do the same for properties.

Any suggestions?

UPD: The exactly task is following:

public class BaseClass {
  public BaseClass(string name) { Name = name; }
  public Name { get; set; }
}
public class Descendant1: BaseClass {
  public Descendant1() : base("Default Name 1") { }
}
...
public class DescendantN: BaseClass {
  public DescendantN() : base("Default Name N") { }
}

I want each of the descendants to have each own DefaultValueAttribute at the Name property with the corresponding default name. And I don't want to hardcode DefaultValueAttribute on each descentand :)

Answer 1

You can't dynamically add or remove attributes. Note that TypeDescriptor doesn't actually add an attribute to the class either: If you check the array that typeof(MyType).GetCustomAttributes(false) returns after you attach your attribute with MyRuntimeAttribute you'll notice that it isn't part of it.

Since you mention design-time, what you can do is dynamically modify attributes. Is that what you actually want to do?

See also:

• http://stackoverflow.com/questions/129285/can-attributes-be-added-dynamically-in-c
• http://stackoverflow.com/questions/2483124/remove-c-attribute-of-a-property-dynamically

Answer 2

You can also provide a control designer and in that designer you can override PreFilterProperties. While typically this is used to hide properties, it can also be used to add them.

http://www.codeproject.com/KB/webforms/HidingProperties.aspx