Question

Hi i’m working on a basic windows form in c# and I have a little problem with the Trim() method.
There are 3 text boxes in witch the user enters his first name, last name and an ID.
Then he can save the info by clicking on a save button but I want to make sure that he doesn’t leave blank boxes so I do the following test:

        string CFN = Curator_FN.Text;
        string CLN = CURATOR_LN.Text;
        string CID = CURATOR_ID.Text;

        Curator_FN.Text.Trim();
        CURATOR_ID.Text.Trim();
        CURATOR_LN.Text.Trim();

        if (((Curator_FN.Text.Length == 0) || (CURATOR_ID.Text.Length == 0) || (CURATOR_LN.Text.Length == 0)))
        {
            MessageBox.Show("You Have to enter a First Name, a Last Name and an ID");
            Empty = true;
        }

The problem is if I just make some blank space with the space bar the Trim() method doesn’t consider them as a blank space..
Maybe I just misunderstand the Trim() method and if I do, do you have any idea on how I could do the this?
Thanks in advance.

Answer 1

The Trim method does not modify the contents of the text boxes, it simply returns the trimmed version. You need to store this version, for example

Curator_FN.Text = Curator_FN.Text.Trim(); 

Of course this has the potential to make changes visible to the user (and it also has to access the UI thread which under other circumstances might be a problem), so it is far better to use a local variable as in

var curatorFn = Curator_FN.Text.Trim(); 
// etc

if (curatorFn.Length == 0 || ... ) {
    // show messagebox
}

Of course if this is all you need to do, using string.IsNullOrWhiteSpace might be a more convenient alternative.