C# edit for number and uppercase letters

Question

In a C# 2010 desktop application I want a textbox field to contain only letters in upper case. In addition I want to allow for numbers. Any other values are not valid for this textbox field. Thus can you show me code on how to setup the edit for uppercase letters and numbers only in the textbox?

Iftikar Hussain · Answer

Hi You can use Leave event of the textbox to check your input. It work for both copy paste and normal typing. this.textBox1.Leave += new System.EventHandler(this.textBox1_TextLeave); private void textBox1_TextLeave(object sender EventArgs e) { var text = textBox1.Text.Trim(); if (Regex.IsMatch(text @^[A-Z0-9]+$)) { // Do something here } else { MessageBox.Show(Doesn't match pattern); } } Regards Iftikar

Vulpes · Answer

Unless you use a custom textbox preventing the user from pasting invalid characters into a textbox isn't easy and many developers just give it up and disable pasting altogether or allow the user to paste anything in and then validate it when focus leaves the textbox. If you use a custom text box (i.e. one which derives from the standard textbox) then all you have to do is to trap the WM_PASTE message examine the clipbpoard contents and reject them if they're invalid. However you then have to remember to use the custom textbox when you need the functionality in question. The KeyChar property returns a char i.e. the unicode character corresponding to the key or combination of keys pressed. As the most commonly used characters are those in the ASCII range you can get their codes from examining an ASCII table: http://www.asciitable.com/ Alternatively you can use a char literal instead of its code: if ((e.KeyChar >= '0' && e.KeyChar = 'A' && e.KeyChar

dc · Answer

The code youy have listed belowTry handling the TextBox's KeyPress event as follows: private void textBox1_KeyPress(object sender KeyPressEventArgs e) { if ((e.KeyChar >= 48 && e.KeyChar = 65 && e.KeyChar e.Handled = true; } Can you tell me where I can look to see what the various values of e.KeyCar means?

dc · Answer

Why would I want to prevent a user from copying and pasting results into the testbox? if they copy and paste the answer would be more correct.

Iftikar Hussain · Answer

what is not working? you need to validate onclick of the button. please tell what pattern is valid and invalid. Regards Iftikar

Vulpes · Answer

No handling the KeyPress event won't prevent the user from copying and pasting invalid characters into the TextBox. However the easiest way to deal with this is to disable pasting altogether either from the context menu (by right clicking the TextBox) or from the keyboard by pressing either Control-V or Shift-Insert. This can be done as follows: public Form1() { InitializeComponent(); textBox1.ContextMenu = new ContextMenu(); // effectively disables context menu } private void textBox1_KeyDown(object sender KeyEventArgs e) { if ((e.Control && e.KeyCode == Keys.V) || (e.Shift && e.KeyCode == Keys.Insert)) { e.SuppressKeyPress = true; } } Regarding Iftikar's approach (i.e. post entry validation) the regular expression is not quite right. It should be: if (Regex.IsMatch(text @^[A-Z0-9]+$)) If you want to allow the TextBox to be left blank replace + with *

dc · Answer

Will keypress work if the user copies and pastes the value into the textbook field

dc · Answer

The following code is not working: if (Regex.IsMatch(text @^[A-Z](\d)+$)) How would yu change the code?

Iftikar Hussain · Answer

Hi You can do this by using Regular Expression private void button1_Click(object sender EventArgs e) { var text = textBox1.Text.Trim(); if (Regex.IsMatch(text @^[A-Z](\d)+$)) { // Do something here } else { MessageBox.Show(Doesn't match pattern); } } Valid - A123 ABC1 ABC111 ABC3783782 AOEIS292999 Invalid - abc 123 abc123 Abc123 Regards Iftikar

Vulpes · Answer

Try handling the TextBox's KeyPress event as follows: private void textBox1_KeyPress(object sender KeyPressEventArgs e) { if ((e.KeyChar >= 48 && e.KeyChar = 65 && e.KeyChar e.Handled = true; }