Don’t let someone tell you that you can’t do it. You can run for president if you want 🙂
For your convenience, this is a fully working example
public class SomeAttribute : Attribute
{
public SomeAttribute(string value)
{
this.Value = value;
}
public string Value { get; set; }
}
public class SomeClass
{
public string Value = "Test";
}
[TestMethod]
public void CanAddAttribute()
{
var type = typeof(SomeClass);
var aName = new System.Reflection.AssemblyName("SomeNamespace");
var ab = AppDomain.CurrentDomain.DefineDynamicAssembly(aName, AssemblyBuilderAccess.Run);
var mb = ab.DefineDynamicModule(aName.Name);
var tb = mb.DefineType(type.Name + "Proxy", System.Reflection.TypeAttributes.Public, type);
var attrCtorParams = new Type[] { typeof(string) };
var attrCtorInfo = typeof(SomeAttribute).GetConstructor(attrCtorParams);
var attrBuilder = new CustomAttributeBuilder(attrCtorInfo, new object[] { "Some Value" });
tb.SetCustomAttribute(attrBuilder);
var newType = tb.CreateType();
var instance = (SomeClass)Activator.CreateInstance(newType);
Assert.AreEqual("Test", instance.Value);
var attr = (SomeAttribute)instance.GetType()
.GetCustomAttributes(typeof(SomeAttribute), false)
.SingleOrDefault();
Assert.IsNotNull(attr);
Assert.AreEqual(attr.Value, "Some Value");
}