A nullable type variable use to a hold null value, which provide the c# language. You can not assign a null value directly to a int type. So to make the value type accept a null value, nullable types are used. You cannot create a nullable type based on a reference type because reference types already support the null value.
Example
using
System;
namespace null_coalescing_operator_in_c_sharp
{
class Program
{
static void Main(string[] args)
{
//define nullable type variable, which value is define null
int? number = null;
// is the hasvalue property which return true or false
try
{
Console.WriteLine(number.Value); //for true
}
catch(System.InvalidOperationException e)
{
Console.WriteLine(e.Message);
}
// if we have provide default value to null able type variable through GetValueOrDefault() function
number = number.GetValueOrDefault();
//then
try
{
Console.WriteLine("\nGet Default Value: {0}", number.Value); //for true
}
catch(System.InvalidOperationException e)
{
Console.WriteLine(e.Message);
}
// if we have provide a value to nullable type variable through user
number = 10;
//then
try
{
Console.WriteLine("\nGet User Value : {0}", number.Value); //for true
}
catch(System.InvalidOperationException e)
{
Console.WriteLine(e.Message);
}
Console.ReadLine();
}
}
}
Output
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