Creating C# Type from full name

I'm trying to get a Type object from type full name i'm doing the folowing:

Assembly asm = Assembly.GetEntryAssembly();  
string toNativeTypeName="any type full name";
Type t = asm.GetType(toNativeTypeName);

I get null, why?

the assembly is my executable (.net executable) and the type name is: System.Xml.XmlNode