Compiler Warning (level 1) CS0183

The given expression is always of the provided ('type') type

If a conditional statement always evaluates to true, then you do not need a conditional statement. This warning occurs when you try to evaluate a type using the is operator. If the evaluation is a value type, then the check is unnecessary.

The following sample generates CS0183:

// CS0183.cs
// compile with: /W:1
using System;
public class Test
{
   public static void F(Int32 i32, String str)
   {
      if (str is Object)          // OK
         Console.WriteLine( "str is an object" );
      else
         Console.WriteLine( "str is not an object" );
      
      if (i32 is Object)   // CS0183
         Console.WriteLine( "i32 is an object" );
      else
         Console.WriteLine( "i32 is not an object" ); // never reached
   }


   public static void Main()
   {

      F(0, "CS0183");
      F(120, null); 
   }
}