Microsoft.CSharp.Nullable Class

The Microsoft.CSharp.Nullable class provides helper methods for working with nullable value types at runtime. It is primarily used by the C# compiler when dealing with the ? nullable modifier.

public static class Microsoft.CSharp.Nullable
{
    public static bool IsNull(object value);
    public static object GetValueOrDefault(object nullable);
    public static object GetValueOrDefault(object nullable, object defaultValue);
}

Methods

IsNull(object value)
Returns true if the supplied value is a boxed nullable type whose HasValue property is false, otherwise false.
GetValueOrDefault(object nullable)
Returns the underlying value of a boxed nullable type, or the default value of the underlying type if HasValue is false.
GetValueOrDefault(object nullable, object defaultValue)
Returns the underlying value of a boxed nullable type, or defaultValue if HasValue is false.

Remarks

All methods accept object parameters to support reflection scenarios where the exact nullable type is not known at compile time.

using System;
using Microsoft.CSharp;

class Program
{
    static void Main()
    {
        int? nullableInt = null;
        object boxed = nullableInt; // boxed nullable

        bool isNull = Nullable.IsNull(boxed);          // true
        int value   = (int)Nullable.GetValueOrDefault(boxed); // 0

        nullableInt = 42;
        boxed = nullableInt;
        isNull = Nullable.IsNull(boxed);               // false
        value = (int)Nullable.GetValueOrDefault(boxed, -1); // 42

        Console.WriteLine($"IsNull: {isNull}, Value: {value}");
    }
}