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entering numbers in c# .NET

Posted on 2009-05-14
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Last Modified: 2012-08-13
hi,
           I have one phone number text box.In that it takes numbers only.it is working fine.i takes only numbers. But Back Space is not working.I post my code
private void txtPhone_KeyPress(object sender, KeyPressEventArgs e)
        {
            int isNumber = 0;
            
            e.Handled = !int.TryParse(e.KeyChar.ToString(), out isNumber);
 
        }

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Question by:mannevenu
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LVL 13

Expert Comment

by:kaylanreilor
ID: 24392792
I think you should "specialize" your text box by using validators:
http://www.codeproject.com/KB/validation/validationprovider.aspx
You can use some masks and the System.Text.RegularExpressions.RegEx class like here: (search for RegEx)
http://www.cornetdesign.com/2008/01/tdd-of-winform-app-part-5-validating.html
See the MSDN doc here : http://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex.aspx

Let's have a look to the System.Text.RegularExpressions namespace and to the System.Windows.Forms.ErrorProvider provider class :
http://msdn.microsoft.com/en-us/library/system.windows.forms.errorprovider.aspx
There are some complete example.

Nevertheless, if you really wants to continu this way, e.KeyChar.ToString() is a string so you can use its Trim methods : http://msdn.microsoft.com/en-us/library/system.string_members.aspx
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Expert Comment

by:kaylanreilor
ID: 24392805
So as I said Trim methods without any argument "Removes all leading and trailing white-space characters from the current String object" : http://msdn.microsoft.com/en-us/library/t97s7bs3.aspx
Probably I can write something like this:
e.Handled = !int.TryParse(e.KeyChar.ToString().Trim(), out isNumber);
 But I'm still convinced that you should develop something like the codeproject article shows above.
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Accepted Solution

by:
Marcjev earned 500 total points
ID: 24392929
Or use something like this validation in a derived textbox or your implementation.
You should only handle your allowed characters though...
public class NumericTextBox : TextBox
{
    bool allowSpace = false;
 
    // Restricts the entry of characters to digits (including hex), the negative sign,
    // the decimal point, and editing keystrokes (backspace).
    protected override void OnKeyPress(KeyPressEventArgs e)
    {
        base.OnKeyPress(e);
 
        NumberFormatInfo numberFormatInfo = System.Globalization.CultureInfo.CurrentCulture.NumberFormat;
        string decimalSeparator = numberFormatInfo.NumberDecimalSeparator;
        string groupSeparator = numberFormatInfo.NumberGroupSeparator;
        string negativeSign = numberFormatInfo.NegativeSign;
 
        string keyInput = e.KeyChar.ToString();
 
        if (Char.IsDigit(e.KeyChar))
        {
            // Digits are OK
        }
        else if (keyInput.Equals(decimalSeparator) || keyInput.Equals(groupSeparator) ||
         keyInput.Equals(negativeSign))
        {
            // Decimal separator is OK
        }
        else if (e.KeyChar == '\b')
        {
            // Backspace key is OK
        }
        //    else if ((ModifierKeys & (Keys.Control | Keys.Alt)) != 0)
        //    {
        //     // Let the edit control handle control and alt key combinations
        //    }
        else if (this.allowSpace && e.KeyChar == ' ')
        {
 
        }
        else
        {
            // Consume this invalid key and beep
            e.Handled = true;
            //    MessageBeep();
        }
    }
 
    public int IntValue
    {
        get
        {
            return Int32.Parse(this.Text);
        }
    }
 
    public decimal DecimalValue
    {
        get
        {
            return Decimal.Parse(this.Text);
        }
    }
 
    public bool AllowSpace
    {
        set
        {
            this.allowSpace = value;
        }
 
        get
        {
            return this.allowSpace;
        }
    }
}

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Expert Comment

by:Anurag Thakur
ID: 24396259
is it a web application or a windows application
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Author Comment

by:mannevenu
ID: 24408938
Windows application
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