Null Coalescing Operator in C#: What It Is and How to Use

The null coalescing operator (??) in C# returns the left-hand operand if it is not null; otherwise, it returns the right-hand operand. It is a simple way to provide a default value when dealing with nullable types or references.

How It Works

Imagine you have a box that might be empty (null) or might contain something. The null coalescing operator checks the box on the left side first. If the box has something inside (not null), it takes that. If the box is empty (null), it takes the item from the right side instead.

This operator helps avoid extra checks like "if this is null, then do that" by combining the check and the fallback in one simple step. It works with nullable types and reference types, making your code cleaner and easier to read.

Example

This example shows how to use the null coalescing operator to provide a default name if the original name is null.

csharp

string? name = null;
string displayName = name ?? "Guest";
Console.WriteLine(displayName);

Output

Guest

When to Use

Use the null coalescing operator when you want to assign a default value if a variable might be null. This is common when reading user input, working with optional data, or handling nullable database fields.

For example, if you get a user's nickname but it might be missing, you can use ?? to show a fallback name instead of dealing with null checks everywhere.

Key Points

• The operator is written as ??.
• It returns the left value if not null; otherwise, the right value.
• It simplifies code by reducing explicit null checks.
• Works with nullable and reference types.

Key Takeaways

The null coalescing operator (??) returns the left operand if not null, else the right operand.

It helps provide default values easily without explicit null checks.

Use it when working with nullable or optional data to simplify your code.

It improves code readability and reduces errors from null references.