How to validate text box numeric type.

Question

Hi! All C# Corner Members. I Have a simple query in .. C# wnidows application In a text box I want to force user to give integer type input. I want simple and shortest code.

Ankit Nandekar · Answer

try this code on key press event private void textBox1_KeyPress(object sender, KeyPressEventArgs e) { if (!(char.IsDigit(e.KeyChar)) ) { e.Handled = true; MessageBox.Show("Enter only digits .", "Alert!"); } }

Nikhil Dhore · Answer

if (char.IsDigit(e.KeyChar) == false && Convert.ToInt32(e.KeyChar) != 8) { MessageBox.Show("Enter Numeric Only."); e.Handled = true; }

Ankit Nandekar · Answer

Welcome santosh.

Santosh Kumar · Answer

Thanks Mr. Nandekar it's working well.

Ankit Nandekar · Answer

santosh my code is working or not?

Muralidharan Deenathayalan · Answer

Please try with KeyDown event. In the keyDown event you will not get char.IsDigit method.

Santosh Kumar · Answer

private void textBox1_KeyPress(object sender, KeyPressEventArgs e) { if (!(char.IsDigit(e.KeyChar)) && (e.KeyCode != Keys.Back || e.KeyCode != Keys.Enter) ) { e.Handled = true; MessageBox.Show("Enter only digits .", "Alert!"); } } During using this code two errors occured: Error 1 'System.Windows.Forms.KeyPressEventArgs' does not contain a definition for 'KeyCode'. Error 2 'System.Windows.Forms.KeyPressEventArgs' does not contain a definition for 'KeyCode' and no extension method 'KeyCode' accepting a first argument of type 'System.Windows.Forms.KeyPressEventArgs' could be found. Please rectify this.

Muralidharan Deenathayalan · Answer

Don't do convert.ToInt for each character, instead of that use e.KeyCode != Keys.Enter like this.

Ankit Nandekar · Answer

Try this if (char.IsDigit(e.KeyChar) == false && Convert.ToInt32(e.KeyChar) != 8 && Convert.ToInt32(e.KeyChar) != 13) { e.Handled = true; MessageBox.Show("Enter only digits.", "Alert!"); }

Muralidharan Deenathayalan · Answer

private void textBox1_KeyPress(object sender, KeyPressEventArgs e) { if (!(char.IsDigit(e.KeyChar)) && (e.KeyCode != Keys.Back || e.KeyCode != Keys.Enter) ) { e.Handled = true; MessageBox.Show("Enter only digits .", "Alert!"); } } I haven't tested this, try this ..

Santosh Kumar · Answer

Thank you Mr. Nandekar for reply private void textBox1_KeyPress(object sender, KeyPressEventArgs e) { if (!(char.IsDigit(e.KeyChar)) ) { e.Handled = true; MessageBox.Show("Enter only digits .", "Alert!"); } } But this code validate Backspae and Enter key also. Which is not required. Please reply ...

Santosh Kumar · Answer

Thank you Mr. Gujrathi. But this code validate Backspae and Enter key also. Which is not required. Please reply...

Muralidharan Deenathayalan · Answer

The simplest way use Regular expression to check the textbox value is numeric or not. using System.Text.RegularExpressions; Regex reg = new Regex(@"^\d+$"); if (!reg.IsMatch(textBox1.Text)) { MessageBox.Show("No Match"); } else MessageBox.Show("Match"); Hope this helps you.

Mayur Gujrathi · Answer

use this public void charonly(KeyPressEventArgs e) { if (Char.IsNumber(e.KeyChar) || Char.IsSymbol(e.KeyChar) || Char.IsWhiteSpace(e.KeyChar) || Char.IsPunctuation(e.KeyChar)) { MessageBox.Show("Only Char are allowed"); e.Handled = true; } } public void digitonly(KeyPressEventArgs e) { try { if (!(char.IsDigit(e.KeyChar) || char.IsControl(e.KeyChar) || char.IsPunctuation(e.KeyChar))) { e.Handled = true; MessageBox.Show("Enter only digit and decimal point.", "Alert!"); } } catch { } } Now call these two methods as per validation type (char or int) from the TextBox KeyPress Event: validation v = new validation(); private void textBox5_KeyPress(object sender, KeyPressEventArgs e) { v.digitonly(e); // allowing interger only } private void textBox1_KeyPress(object sender, KeyPressEventArgs e) { v.charonly(e); // allowing character only }