Back Space Button is not working

Alok Pandey

Hi,

I am trying to provide validation on textbox that it accept only digits. it executes properly by following c# code
on textbox keypress event,

if(!(char.IsDigit (e.KeyChar)))
{
e.Handled = true;
}

But back space button is also not working on this. I Want, Back Space button work on textbox.
Where is the Problem In my Code?

Thanks in Advance

10 Replies

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Jignesh Kumar5y ago
Hi Alok,

Please find below link which will help you,
https://www.programmersought.com/article/6036438250/
https://stackoverflow.com/questions/1523895/how-to-get-backspace-with-only-numbers-limit-in-textbox
+1
Amit Mohanty5y ago
Hey, try the 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;
    }
}
+1
S J5y ago
private void txtX_KeyPress(object sender, KeyPressEventArgs e)
{
if (!(Char.IsDigit(e.KeyChar) || (e.KeyChar == (char)Keys.Back)))
e.Handled = true;
}

It works for both accept only integer and backspace also works...
+1
Rajanikant Hawaldar5y ago
Below code accepts numbers and backspace.
private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
     if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar))
{
e.Handled = true;
}
}
+1
S J5y ago
same error, i need allow textboxes only digits with backspac
+1
Sonu Gupta5y ago
C# Code For Digit only with backspace:

e.Handled = !Char.IsNumber(e.KeyChar) && e.KeyChar != 8;

JavaScript Code For Digit only with backspace:

function DigitOnly(e) { if (navigator.appName != "Netscape") { e = e || window.event; if (e.keyCode > 47 && e.keyCode < 58) { } else { return false; } } else { e = e || window.event; if (e.charCode > 47 && e.charCode < 58) { } else if (e.charCode == 0) { } else { return false; } } }

Calling method:

+1
S J5y ago
hi priya
Backspace is working but, it accepting charcters also......
textboxes accept only intigers and allow for backspace ,delete keys in keypress event
+1
Jonathas Sucupira15y ago
Why not use the built in RegularExpressionValidator?
+1
Vilas Gite15y ago
Hi Alok, Welcome here,

Refer:

http://social.msdn.microsoft.com/Forums/en-US/Vsexpressvb/thread/3000c21c-c0ad-4c04-afca-6b16833804a6/

Thanks.

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+1
Priya Linge15y ago
Hi,

Please try this,

if (e.KeyChar == (char)Keys.Back && !(char.IsControl(e.KeyChar)))
            {
                e.Handled = true;

            }

Use !Char.IsControl(e.KeyChar) so that all the "control" characters like the backspace key and clipboard keyboard shortcuts are exempted.

IsControl :Indicates whether a specified Unicode character is categorized as a control character.

Hope this will help you.

Thanks.
+2