how to validate textbox that accepts only integers

S J

how to validate textbox that accepts only integers with backspace wants to work in c# windows application.

i wrote keypress event its working for integers but backspace is not working.

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Hey, please check below code.

//1. allowed only numeric value ex.10
private void Number_KeyPress(object sender, KeyPressEventArgs e)
{
//allowed only numeric value ex.10
if (e.KeyChar >= 48 && e.KeyChar <= 57 || e.KeyChar == 8)
{
e.Handled = false;
}
else
{
e.Handled = true;
}
}
//2. allowed numeric and one dot ex. 10.23
private void Numeric_KeyPress(object sender, KeyPressEventArgs e)
{
// allowed numeric and one dot ex. 10.23
if (e.KeyChar >= 48 && e.KeyChar <= 57 || e.KeyChar == 8 || e.KeyChar == 46)
{
e.Handled = false;
}
else
{
e.Handled = true;
}
// only allow one decimal point
if (e.KeyChar == 46 && (sender as TextBox).Text.IndexOf('.') > -1)
{
e.Handled = true;
}
}
//3. Allow only allow one decimal point, negative number and backspace
private void NumberNegitive_KeyPress(object sender, KeyPressEventArgs e)
{
if (e.KeyChar >= 48 && e.KeyChar <= 57 || e.KeyChar == 46 || e.KeyChar == 45)
{
e.Handled = false;
}
else
{
e.Handled = true;
}
// only allow one decimal point
if (e.KeyChar == 46 && (sender as TextBox).Text.IndexOf('.') > -1)
{
e.Handled = true;
}
// allow negative
Regex reg = new Regex(@"^-?\d+[.]?\d*$");
if (!reg.IsMatch((sender as TextBox).Text.Insert((sender as TextBox).SelectionStart, e.KeyChar.ToString()) + "1"))
{
e.Handled = true;
}
// allow backspace
if (e.KeyChar == 8)
{
e.Handled = false;
}
}

You can take advantage of numerucUpDown control that was made for this purpose only

Hello Shipa,

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
e.Handled = !Char.IsNumber(e.KeyChar) && e.KeyChar != 8; //8 is allow the backspace
}

Thanks

If you want to allow only numerics and backspace then the Key_Press event should be

Here is the code to check if backspace is pressed

Below code accepts numbers and backspace.