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Compiler Error CS0034

Operator 'operator' is ambiguous on operands of type 'type1' and 'type2'

An operator was used on two objects and the compiler found more than one conversion. Conversions need to be unique, so you either need to make a cast or to make one of the conversions explicit.

The following sample generates CS0034:

// CS0034.cs
public class A
{
   // allows for the conversion of A object to int
   public static implicit operator int (A s)
   {
      return 0;
   }

   public static implicit operator string (A i)
   {
      return null;
   }
}

public class B
{
   public static implicit operator int (B s)
   // one way to resolve this CS0034 is to make one conversion explicit
   // public static explicit operator int (B s)
   {
      return 0;
   }

   public static implicit operator string (B i)
   {
      return null;
   }

   public static implicit operator B (string i)
   {
      return null;
   }

   public static implicit operator B (int i)
   {
      return null;
   }
}

public class C
{
   public static void Main ()
   {
      A a = new A();
      B b = new B();
      b = b + a;   // CS0034
      // another way to resolve this CS0034 is to make a cast
      // b = b + (int)a;
   }
}
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