Q: What's wrong with the below generic class?

VB.NET
Imports System.Data
Imports System.Web

Public Class GenericClass(Of T As DataTable)
   Public Function GetValue(ByVal val As T) As T
      Return val
   End Function

   Public Function GetValue(ByVal val As T) As DataTable
      Return val
   End Function

   Public Sub GetValue(ByVal val As T)
      HttpContext.Current.Response.Write(val)
   End Sub
End Class

C#
using System.Data;
using System.Web;

public class GenericClass<T> where T : DataTable
{
   public T GetValue(T val)
   {
      return val;
   }

   public DataTable GetValue(T val)
   {
      return val;
   }

   public void GetValue(T val)
   {
      HttpContext.Current.Response.Write(val);
   }
}

A: At first glance, the overloaded methods appear to be unique. However, this is not the case. In VB.NET, the first 2 methods would error and in C# the last 2 methods would error. Why does this happen? Like non-generic methods, your generic methods must be unique by their method signatures, not just by their return types.