String Performance: Checking for An Empty String

Updated January 2024

String validation is a widespread practice when evaluating user input or data received from API requests. In the course of my code reviews, I often come across situations where developers persist in using the following code to ascertain if a string variable contains a value.

if (emailAddress == "")

This could potentially pose a performance issue and might lead to an exception later on if the string is null. The more efficient and exception-resistant approach is to utilize one of the following methods from the String type:

• IsNullOrEmpty(): Introduced in the .NET Framework 2.0
• IsNullOrWhiteSpace(): Introduced in the .NET Framework 4.0

Here is an illustrative example.

if (string.IsNullOrEmpty(emailAddress))

Both methods return a Boolean value, and, notably, they will never result in an exception. Here are alternative approaches that developers commonly use to check for an empty string.

if (emailAddress?.Length == 0)

or

if (emailAddress == null || emailAddress == string.Empty)

or pattern matching can also be used:

if (emailAddress is { Length: > 0 })

Benchmark

From the results, it is evident that employing IsNullOrEmpty() is more efficient than other methods for checking an empty string.

When I setup the code analysis in my EditorConfig it looks like this: dotnet_diagnostic.CA1820.severity = warning

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