Compiler Error CS0031

Constant value 'value' cannot be converted to a 'type'. (use 'unchecked' syntax to override)

An attempt was made to assign a value to a variable whose type cannot store the value. For more information, see Types (C# Programming Guide).

The following sample generates CS0031 in both checked and unchecked contexts:

// CS0031.cs
namespace CS0031
{
   public class a
   {
      public static void Main()
      {
         int num = (int)2147483648M; //CS0031
         // Try using a larger numeric type instead:
         // long num = (long)2147483648M; //CS0031

         const decimal d = -10M; // Decimal literal
            unchecked
            {
                const byte b = (byte)d; // CS0031
                // For small values try using a signed byte instead:
                // const sbyte b = (sbyte)d;
            }
      }
   }
}

See Also

Reference

unchecked (C# Reference)