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Compiler Error CS1601

  • Article

Method or delegate parameter cannot be of type 'type'

Some types in the .NET Framework class library, for example, TypedReference, RuntimeArgumentHandle and ArgIterator cannot be used as ref or out parameters because they could potentially be used to perform unsafe operations.

The following sample generates CS1601:

// CS1601.cs
using System;

class MyClass
{
   public void Test1 (ref TypedReference t)   // CS1601
   {
   }

   public void Test2 (out ArgIterator t)   // CS1601
   {
   }
}