Allow only number no Letters?

Question

Hi all,

How do I make a question that only accepts numbers and not letters.

For example.

Enter your age:

Twelve

"Please enter your age in numeric form.

I assume that this is done by some sort of if statement?

Any help would be great.

Cheers.

Answer 1

This should do the trick:

PS: the code has no warnings, only does let youtype integers.

    bool bJumping;
    private void textBox1_TextChanged(object sender, EventArgs e)
    {
      if (!bJumping)
      {
        int intValue = 0;
        string strValue = textBox1.Text;
        if (!String.IsNullOrEmpty(strValue))
        {
          bool bChecking = int.TryParse(strValue, out intValue);
          if (!bChecking)
          {
            bJumping = true;
            textBox1.Text = strValue.Remove(strValue.Length - 1, 1);
            textBox1.SelectionStart = textBox1.Text.Length;
          }
        }
      }
      else
        bJumping = false;
    }

Answer 2

Example three gives a very clear way to handle this.

 

http://msdn.microsoft.com/en-us/library/system.windows.forms.keyeventargs.aspx

 

 

---

Devlin Liles

Answer 3

u can use the keypress event on u r textbox:

private void txtAge_KeyPress(object sender, KeyPressEventArgs e)
        {
            if (char.IsDigit(e.KeyChar) || (int)e.KeyChar == 8) // second expression is for backspace
                e.Handled = false;
            else
                e.Handled = true;

        }

---

Thanks, Srinivasa Rao Dhulipalla
Mark As Answer if it helped you.

Answer 4

You can also use this method:

try
      {
        if (!Char.IsDigit(e.KeyChar)) e.Handled = true;

        if (e.KeyChar == '\b') e.Handled = false; //allow Backspace

        if (e.KeyChar.Equals('-') && TxtBPrice.SelectionStart == 0) e.Handled = false; //allow negative number

        if (e.KeyChar.Equals('.') && TxtBPrice.Text.IndexOf(".") == -1) e.Handled = false; //allow single decimal point

        if (e.KeyChar == '\r') TxtBPrice.Focus(); //Enter key moves to next control
      }
      catch
      {
      }

---

www.midnightprogramer.net

Answer 5

you can read the example in this tutorial which is the solution of your problem,

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.keypress.aspx

i m typing here too,

// Boolean flag used to determine when a character other than a number is entered.
        private bool nonNumberEntered = false;

        // Handle the KeyDown event to determine the type of character entered into the control.
        private void textBox1_KeyDown(object sender, System.Windows.Forms.KeyEventArgs e)
        {
            // Initialize the flag to false.
            nonNumberEntered = false;

            // Determine whether the keystroke is a number from the top of the keyboard.
            if (e.KeyCode < Keys.D0 || e.KeyCode > Keys.D9)
            {
                // Determine whether the keystroke is a number from the keypad.
                if (e.KeyCode < Keys.NumPad0 || e.KeyCode > Keys.NumPad9)
                {
                    // Determine whether the keystroke is a backspace.
                    if(e.KeyCode != Keys.Back)
                    {
                        // A non-numerical keystroke was pressed.
                        // Set the flag to true and evaluate in KeyPress event.
                        nonNumberEntered = true;
                    }
                }
            }
            //If shift key was pressed, it's not a number.
            if (Control.ModifierKeys == Keys.Shift) {
                nonNumberEntered = true;
            }
        }

        // This event occurs after the KeyDown event and can be used to prevent
        // characters from entering the control.
        private void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
        {
            // Check for the flag being set in the KeyDown event.
            if (nonNumberEntered == true)
            {
                // Stop the character from being entered into the control since it is non-numerical.
                e.Handled = true;
            }
        }

or you can try this method too...

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
if (Char.IsDigit(e.KeyChar) )
{ MessageBox.Show("only numbers are allowed");
e.Handled = true; ;
}
}

Answer 6

Hello guys,

 

Or you can always create a custom TextBox control which takes an enumeration of InputType in which you can specify what chars are accepted in the textbox, something like this:

  public class CustomTextBox : TextBox
  {
    public InputTypeEnum InputType { get; set; }

    protected override void OnKeyPress(KeyPressEventArgs e)
    {
      if (e.KeyChar != '\b')
      {
        switch (InputType)
        {
          case InputTypeEnum.Text:
            e.Handled = !Char.IsLetter(e.KeyChar);
            break;
          case InputTypeEnum.Numeric:
            e.Handled = !Char.IsDigit(e.KeyChar);
            break;
        }
      }

      base.OnKeyPress(e);
    }
  }

  public enum InputTypeEnum
  {
    Text,
    Numeric
  }

Hope this helps, if you have any other questions or comments, please let me know,

Best Regards,
Emanuel Varga
Telerik WinForms MVP

---

If a post answers your question, please click "Mark As Answer" on that post and "Mark as Helpful".

Answer 7

hi Alexander.

following code is very simple & short solution :

you only need for following block code that uses from KeyPress event of TextBox:

   private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
    {
      if (e.KeyChar >= 48 && e.KeyChar <= 57)
        textBox1.Text += e.KeyChar;

      else if (e.KeyChar == 8 && textBox1.Text.Length > 0) // earse textBoxNumber with BackSpace key
        textBox1.Text = textBox1.Text.Remove(textBox1.Text.Length - 1);

      textBox1.SelectionStart = textBox1.Text.Length;
    }

---

.Net adventurer

If (a post answers your question) {please click " Mark As Answer" and "Mark as Helpful" on that post} 

Answer 8

thanks a lot for your code