.NET Tips and Tricks

Blog archive

New in Visual C# 6.0, Visual Basic 14: New Null/Nothing Check

I don't know how many times I've written this code like this:

if (stringVariable != null)
{
  int x = stringVariable.Length;
}

In Visual Basic I'd write this:

If stringVariable IsNot Nothing then
  Dim x as Integer 
  x = stringVariable.Length
End If

I test the string for null/nothing because if I try to get the Length of a variable set to null/Nothing ... well, I don't get the string's Length (null values don't have lengths). Instead, I get an exception.

To simplify this block of code, both C# 6.0 and Visual Basic 14 add a new operator that you can tack onto the end of a string (or other values): the question mark (?). If the string that the operator is added to is null then the expression returns null and no further processing happens.

This means that I could rewrite my previous code like this:

int x = stringVariable?.Length;

If stringVariable is set to null or Nothing, processing ends at the ? mark and no attempt is made to retrieve the Length value ... which means no exception is raised.

However, my code still isn't right because, after all, the expression with the ? operator has to return something. If my string is null then the ? operator will return null ... and my code has to handle that. The solution is to use a nullable data type to catch the result of my expression. For my example, the final code looks like this:

Dim x As Integer? = stringVariable?.Length

Two other items: First, you can use the ? operator with types other than strings. Second, if you think the ? operator is useful, consider looking at the string object's IsNullOrWhiteSpace method.

Posted by Peter Vogel on 05/04/2015 at 11:05 AM


comments powered by Disqus

Featured

  • Top 3 Blazor Extensions for Visual Studio Code

    Some developers prefer to create applications with Microsoft's open-source Blazor tooling from within the open-source, cross-platform Visual Studio Code editor. Here are the top tools in the VS Code Marketplace for those folk, as measured by the number of installations.

  • How to Invert a Machine Learning Matrix Using C#

    VSM Senior Technical Editor Dr. James McCaffrey, of Microsoft Research, explains why inverting a matrix -- one of the more common tasks in data science and machine learning -- is difficult and presents code that you can use as-is, or as a starting point for custom matrix inversion scenarios.

  • Microsoft Engineer: 'It's Time to Move OData to .NET 5'

    Microsoft engineer Sam Xu says "it’s time to move OData to .NET 5" and in a new blog post he shows how to do just that.

  • Microsoft Goes Virtual with Developer Education in Face of COVID-19

    Like many organizations that host developer educational events, Microsoft has gone virtual amid shelter-in-place directives and a surge in remote work stemming from the COVID-19 pandemic.

  • Microsoft Enhances Low-Code Power Apps

    Microsoft's nod to the low-code movement, Power Apps, has been enhanced with a bevy of new features, including mixed reality, canvas/model support in a new mobile app, UX improvements and more.

.NET Insight

Sign up for our newsletter.

Terms and Privacy Policy consent

I agree to this site's Privacy Policy.

Upcoming Events