How to check if a lambda expression has not been assigned?

Question

I have a problem with my code. I'm doing a crud with C# and I'm tring to find a student by id. In case you do not find any match I want to send a message saying that there is no student with that id. How can I do that?

I tried with a simple while:

while(i < count && !found)
{
    s = studentList[i];
    if (id.Equals(s.IdStudent))
    {
        found = true;
        student = s;
    }
    i++;
}

if (found == false)
{
    System.Console.WriteLine("There is no match");
}

And I'm trying this:

student = studentList.First(i => i.IdStudent == id);
if(student == null)
{
    System.Console.WriteLine("There is no match");
}

It seems to be fine but when executing and using an id that is not in the list it tells me that I do not control the exception.

Try `FirstOrDefault` instead of `First` and your code should work. — oerkelens, Feb 16 '19 at 10:15

score 1 · Accepted Answer · answered Feb 16 '19 at 10:16

1

If you use First, the expectation is that there is at least one element in the sequence. Using FirstOrDefault should be fine for your case.

answered Feb 16 '19 at 10:16

Janez Lukan

1,439
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score 1 · Answer 2 · answered Feb 16 '19 at 10:17

1

You need to use FirstOrDefault instead of First.

answered Feb 16 '19 at 10:17

Amir Molaei

3,700
1
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20

How to check if a lambda expression has not been assigned?

2 Answers2