Don't allow a specific use of characters

Question

I bumped into a problem, i hope someone can help me out :)
I got a TextBox, and i want to limit users, so that they can't write multiple \ one after another.
I'm using it for folders. For instance: C\temp\test\
Now I want to prevent input like: C\temp\test\\\

I've tried searching around for this problem, but I couldn't find anything like this, so I hope it's possible :)

I don't really have any code to show, but here's the code for my TextBox:

    private void textBox1_TextChanged(object sender, EventArgs e)
    {
        try
        {
            Regex regex = new Regex(@"[^C^D^A^E^H^S^T^]");
            MatchCollection matches = regex.Matches(textBox1.Text);
            if (matches.Count > 0)
            {
                MessageBox.Show("Character niet toegestaan!");
                textBox1.Text = "";
            }

            clsOpslagMedium objOpslag;  // definieert type object 
            objOpslag = new clsOpslagMedium();  // creert opject in memory
            objOpslag.DriveLetterString = textBox1.Text;
        }
        catch (Exception variableEx1)
        {
            MessageBox.Show("Foutmelding: " + variableEx1.Message);
        }
    }

I hope I provided enough information :)

The quality control procedure is likely trying to save us from a question with no code to show initial effort. — Grant Thomas, Jun 19 '13 at 14:03
possible duplicate of [C# - TextBox Validation](http://stackoverflow.com/questions/6404947/c-sharp-textbox-validation) — nvoigt, Jun 19 '13 at 14:03
Do you want to make it impossible for someone to write it from the beginning, or do you wish validate it once it has been changed? — Sander, Jun 19 '13 at 14:04
"just typing some extra text here because the question body does not meet quality standards.. lol" Just downvoting here because the question does not meet quality standards.. lol — Pierre-Luc Pineault, Jun 19 '13 at 14:04
possible duplicate of [Textbox don't allow typing " \ " 2 times after each other](http://stackoverflow.com/questions/17193770/textbox-dont-allow-typing-2-times-after-each-other) — John Kraft, Jun 19 '13 at 14:24
@JohnKraft No, it's actually the other way around. The question you're linking to is actually an exact duplicate of this one. — Nolonar, Jun 19 '13 at 14:27

Ahmed KRAIEM · Answer 1 · 2013-06-19T14:40:17.567

0

If the textbox contains \\, it is invalid:

if (textBox1.Text.Contains(@"\\"))
{
     MessageBox.Show("Error!");
}

edited Jun 19 '13 at 14:40

answered Jun 19 '13 at 14:28

Ahmed KRAIEM

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@X.L.Ant I almost, ***almost*** downvoted this answer for putting a wrong answer. `textBox1.Text.Contains("\\")` will always hold true, when you write paths into `textBox1`. The original answer was correct. – Nolonar Jun 19 '13 at 14:32
Shouldn't this be `textBox1.Text.Contains(@"\\")` or `textBox1.Text.Contains("\\\\"))`? edit; you fixed it and I am a slow typer. – AutomatedChaos Jun 19 '13 at 14:34
Hey, it doesn't work. i hope you can help me out som further. i tried doing if (textBox2.Text.Contains("\\, \\, \\\\, \\\\, \\\\, \\\\\\, \\\\\\\\")) { MessageBox.Show("error"); } – Ricje20 Jun 19 '13 at 14:34
@Ricje20 you know, '\\\' contains '\\' as do '\\\\' and so on... no need to test anything else than '\\'. Just try with what's provided. – xlecoustillier Jun 19 '13 at 14:39
@Ricje20 Your `Contains` will only return true, if your TextBox contains that string, for instance: `"hello \\, \\, \\\\, \\\\, \\\\, \\\\\\, \\\\\\\\ world"` would work, but not `"hello \\ world"` or `"hello \\\\ world"` – Nolonar Jun 19 '13 at 14:43

Don't allow a specific use of characters

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