CODEWITHSUNDEEP
c#regexwinformstextbox
user3036459
user3036459

Reputation:

C# - Textbox with only letters and numbers

How can I limit my textbox to only accept numbers and letters? It should not even allow spaces or anything like "!", "?", "/" and so on. Only a-z, A-Z, 0-9

Tried this and it did not work at all 

if (System.Text.RegularExpressions.Regex.IsMatch(@"^[a-zA-Z0-9\_]+", txtTag.Text))
{
    txtTag.Text.Remove(txtTag.Text.Length - 1);
}

Not even sure if that txtTag.Text.Remove(txtTag.Text.Length - 1); should be there because it makes the application crash.

Upvotes: 2

Views: 29641

Answers (5)

gg mm
gg mm

Reputation: 13

try this code for the letter and numbers:

Void textbox1_KeyPress(object sender,KeyPressEventArgs e) {

// allows only letters or numbers
if (!Char.IsLetterOrDigit(e.KeyChar))
{
    e.Handled = true;
}

}

Upvotes: 0

Ali Ismayilov
Ali Ismayilov

Reputation: 63

try this

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
    {
        e.Handled = !char.IsLetter(e.KeyChar) && !char.IsControl(e.KeyChar)
             && !char.IsSeparator(e.KeyChar) && !char.IsDigit(e.KeyChar) && !char.IsControl(e.KeyChar);
    }

Upvotes: 2

Michael Di Felice
Michael Di Felice

Reputation: 406

My thought is you could alter the KeyPressed or TextChanged events for that control to check if the characters entered are numbers or letters. For example, to check the characters as they are added in the textbox you could do something like the following :

myTextbox.KeyPress += new KeyPressEventHandler(myTextbox_KeyPress);



void myTextbox_KeyPress(object sender, KeyPressEventArgs e)
{
    if(e.KeyChar >= Keys.A && e.KeyChar <= Keys.Z)

    // you can then modify the text box text here

Upvotes: 1

albusshin
albusshin

Reputation: 4010

First of all, check out this article for some information.

I think what you should do on the client side is to add the pattern attribute in the corresponding HTML.

<input type="text" name="foo" pattern="[a-zA-Z0-9_]" title="Please input only letters and numbers">

Upvotes: -2

Pierre-Luc Pineault
Pierre-Luc Pineault

Reputation: 9201

You don't need a regex for that:

        textBox1.Text = string.Concat(textBox1.Text.Where(char.IsLetterOrDigit));

This will remove everything that is not a letter or digit, and can be placed in the TextChanged event. Basically, it gets the text, splits it into characters and only pick what is a letter or digit. After that, we can concatenate it back to a string.

Also, if you'd like to place the caret at the end of the textbox (because changing the text will reset its position to 0), you may also add textBox1.SelectionStart = textBox1.Text.Length + 1;

Upvotes: 11

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