Restricting textbox input to numbers in C# [closed]

Answer 1

The most crude down and dirty way of doing it is doing something like this:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        this.textBox1.KeyPress += new KeyPressEventHandler(textBox1_KeyPress);
    }

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

}

You're still not safe with this approach, as users can still copy and paste non-numeric characters into the textbox. You still need to validate your data regardless.

Answer 2

You can use the FilterTextBox of AJAX Control Toolkit. Using this you can allow/disallow any character type. This is quite flexible.

Answer 3

You can use the Microsoft.VisualBasic.Information.IsNumeric is numeric function. Just add the reference Microsoft.VisualBasic

private void textBox1_Validating(object sender,
        System.ComponentModel.CancelEventArgs e) {
    if (!Microsoft.VisualBasic.Information.IsNumeric(textBox1.Text)) {
        e.Cancel = true;
    } else {
        // Do something here
    }
}

This allows the user to enter scientific notation which is not trivial to filter for.

Answer 4

Have you tried the MaskedTextBox control in WinForms?

Answer 5

Have a look at something like this

Masked C# TextBox Control

Answer 6

has some bugs but easy way :D

 private void textbox1_TextChanged(object sender, EventArgs e)
        { 
            char[] originalText = textbox1.Text.ToCharArray();
            foreach (char c in originalText)
            {
                if (!(Char.IsNumber(c)))
                {
                    textbox1.Text = textbox1.Text.Remove(textbox1.Text.IndexOf(c));
                    lblError.Visible = true;
                }
                else
                    lblError.Visible = false;
            }
            textbox1.Select(textbox1.Text.Length, 0);
        }