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What operators C# provides to deal with null values?
C# has the following three operators to deal with the null values −
null-coalescing operator (??)
Allows you to get the value of a variable if it's not null, alternatively specifying 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 that illustrates 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 (??=)
It returns the value on the left side if it's not null. Otherwise, it returns the value on the right side. 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";
with the following expression.
result ??= "default_value";
This operator is useful with lazily calculated 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 call a method on an instance safely. If the instance is null, it returns null instead of throwing NullReferenceException. Otherwise, it simply calls the method.
It replaces the following expression in C# −
string result = instance == null ? null : instance.Method();
with 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
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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