How to check for null value in LINQ

Question

2.00/5 (1 vote)

See more:

Hi, I'm trying to put an if statement after the from clause in this query and check variable t:

C#

if(t == null)
   do nothing;
else
   select new TaskViewModel(t, this)).ToList<TaskViewModel>());

C/

vmSubTasks = new List<TaskViewModel>(
                (from t in vmTask.SubTasks
                 select new TaskViewModel(t, this)).ToList<TaskViewModel>());

Can I put a where clause? (where t != null)
I also want to check vmTask.SubTasks before use.

Posted 19-Oct-12 23:55pm

cs101000

Updated 20-Oct-12 5:58am

Yvan Rodrigues

v5

Add a Solution

Comments

vasim sajad 20-Oct-12 9:34am

vmTask.SubTasks datatype ?

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sandeep Mewara · Answer 1 · 2012-10-19T23:58:00

Solution 1

Here: Checking for possibly null values in LINQ[^]

Something like:

C#

var titleless = title == null ?
  items.Where(x => x.Title == null) : items.Where(x => x.Title == title);

Posted 19-Oct-12 23:58pm

Sandeep Mewara

Comments

cs101000 20-Oct-12 6:21am

I think this example is not my case, I improved the question.

Yvan Rodrigues · Answer 2 · 2012-10-20T05:55:00

vmSubTasks = vmTask.SubTasks == null 
    ? null 
    : (from t in vmTask.SubTasks
       where t != null
       select new TaskViewModel(t, this))
    .ToList<taskviewmodel>();</taskviewmodel>

or

vmSubTasks = vmTask.SubTasks == null 
    ? null 
    : vmTask.SubTasks
          .Where(t => t != null)
          .Select new TaskViewModel(t, this)
          .ToList<taskviewmodel>();</taskviewmodel>

Note that in your code snippet you are creating a list twice. The first is passed to the constructor of the second.