C# - test and cast with reference type or value...

Please check the following code snippet for test and cast on references types (exemplified by a string object), or a value type , represented by a int type.

also, the special case of 0 is considered.

[Test]
public void TestConvertNullToString()
{
var a = ((string) null);
if (a == null)
{
Console.WriteLine("Hello");
}
else
{
Console.WriteLine("bbb");
}

if (a is string)
{
Console.WriteLine("a is String");
}
else
{
Console.WriteLine("a is not String");
}

if (a is int)
{
Console.WriteLine("a is int");
}
else
{
Console.WriteLine("a is not int");
}

//            if ((a as int) == null)
//            {
//                Console.WriteLine("a is not String");}
//
//            }
//            else
//            {
//               Console.WriteLine("a is not String");
//            }

int c = 1;
object d = c;
a = ((string) d); // Invalid cast exception

Assert.DoesNotThrow(() => { string.IsNullOrEmpty((string) null); });
}
}
}