If you want to expose all properties, methods, and events that are associated with a type as scriptable, use the ScriptableTypeAttribute class instead.

The following example shows how you make a property, method, or event (PME) scriptable by applying the ScriptableMemberAttribute immediately before the name of the PME.

public class SMT_ScriptableManagedType
    {
    [ScriptableMember]         // This is the preferred syntax
     public string GetString()
        { return "abcdefg"; }

    [ScriptableMemberAttribute]  // This is also acceptable
     public string GetString()
        { return "abcdefg"; }
}

For information on the operating systems and browsers supported by Silverlight, see "Supported Operating Systems and Browsers" in Silverlight Architecture.

Reference