C# Error CS1959 – ‘{0}’ is of type ‘{1}’. The type specified in a constant declaration must be sbyte, byte, short, ushort, int, uint, long, ulong, char, float, double, decimal, bool, string, an enum-type, or a reference-type.

C# Error

CS1959 – ‘{0}’ is of type ‘{1}’. The type specified in a constant declaration must be sbyte, byte, short, ushort, int, uint, long, ulong, char, float, double, decimal, bool, string, an enum-type, or a reference-type.

Reason for the Error & Solution

‘name’ is of type ‘type’. The type specified in a constant declaration must be sbyte, byte, short, ushort, int, uint, long, ulong, char, float, double, decimal, bool, string, an enum-type, or a reference-type.

The types permitted in a const declaration are limited to those described in this message.

To correct this error

  1. Declare the constant with an allowed type.

Example

The following code produces CS1959 because null is not a type.

// cs1959.cs  
class Program  
    {  
        static void Test<T>() where T : class  
        {  
            const T x = null; // CS1959  
        }  
    }