Best practices for null checks in C#

Null_check_C#

In C# applications, null reference exceptions are frequently the cause of problems and runtime failures. Appropriate null checks are necessary to protect your code from these kinds of problems. This article will examine many approaches to doing null checks in C#, go over the recommended approach, and provide examples to show how to use each one.

1. Traditional null check:

The most straightforward way to check for null is through an explicit comparison. For instance:

if (variable != null)
{
    // Do something with variable
}

Use the is not null operator to check for null values. The is not null operator is a safe way to check for null values, even if the not equality operator (!= null) has been overridden.

if (variable is not null)
{
    // Do something with variable
}

If you are writing code that needs to be compatible with older versions of C#, you should use != null, because the is not null operator was not introduced until C# 9.

Here are some examples of when to use is not null and != null:

// Use `is not null` if you are working with code that you do not control.
object obj = GetObjectFromSomewhere();
if (obj is not null)
{
  // Do something with the object.
}

// Use `!= null` if you are working with code that you control, and you know that the equality operator has not been overloaded.
string name = GetName();
if (name != null)
{
  // Do something with the name.
}

// Use `!= null` if you need to be compatible with older versions of C#.
int? number = GetNumber();
if (number != null)
{
  // Do something with the number.
}

While this method is simple and widely used, it can be error-prone, especially in large codebases where developers might forget to include null checks, leading to unexpected crashes.

2. Conditional Access Operator (?.):

Introduced in C# 6.0, the conditional access operator is a powerful tool that can help you to write more concise and robust code. By using the conditional access operator, you can avoid having to write explicit null checks for every reference type that you access. For example:

// Access a member of a class.
Person person = GetPerson();
string name…