What operators does C# provide to handle null values?

C# has the following three operators to handle null values ​​-

Null coalescing operator (??)

allows you to get the value of a variable (if not) null, or specify a default value that can be used.

It replaces the following expression in C# -

string resultOne = value != null ? value : "default_value";

with the following expression -

string resultTwo = value ?? "default_value";

Here is an example illustrating this.

Example

using System;
class Program{
   static void Main(){
      string input = null;
      string choice = input ?? "default_choice";
      Console.WriteLine(choice); // default_choice
      string finalChoice = choice ?? "not_chosen";
      Console.WriteLine(finalChoice); // default_choice
   }
}

Null coalescing assignment operator (??=)

If the value on the left is not null, return the value. Otherwise, it returns the value on the right. In other words, it allows you to initialize a variable to some default value if its current value is null.

It replaces the following expression in C# -

if (result == null)
result = "default_value";

Use the following expression.

result ??= "default_value";

This operator is useful for lazily computed properties. For example -

Example

class Tax{
   private Report _lengthyReport;
   public Report LengthyReport => _lengthyReport ??= CalculateLengthyReport();
   private Report CalculateLengthyReport(){
      return new Report();
   }
}

Null Conditional Operator (?.)

This operator allows you to safely call methods on an instance. If the instance is null, return null instead of throwing a NullReferenceException. Otherwise, it just calls the method.

It replaces the following expression in C# -

string result = instance == null ? null : instance.Method();

Use the following expression -

string result = instance?.Method();

Consider the following example.

Example

using System;
string input = null;
string result = input?.ToString();
Console.WriteLine(result); // prints nothing (null)

Example

Real-time demonstration

using System;
class Program{
   static void Main(){
      string input = null;
      string choice = input ?? "default_choice";
      Console.WriteLine(choice); // default_choice
      string finalChoice = choice ?? "not_chosen";
      Console.WriteLine(finalChoice); // default_choice
      string foo = null;
      string answer = foo?.ToString();
      Console.WriteLine(answer); // prints nothing (null)
   }
}

Output

default_choice
default_choice

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