Restricting textbox input to numbers in C# [closed]

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开发者_如何学C

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I want to restrict a textbox to accept only numbers in C#. How do I do that?

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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.

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From others have said before me, we have to almost know what you will use this in, WinForms, ASP.NET, Silverlight ...

But now I take a chance that it is WinForm:)

private void TxtBox1_KeyPress(object sender, KeyPressEventArgs e)
{
     if (!System.Text.RegularExpressions.Regex.IsMatch(e.KeyChar.ToString(), "\\d+"))
          e.Handled = true;
}

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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);
        }

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Have you tried the MaskedTextBox control in WinForms?

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Have a look at something like this

Masked C# TextBox Control

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This may not be the best way, but works ok for WPF TextBox...

    private void textBox1_TextChanged(object sender, TextChangedEventArgs e)
    {
        string originalText = ((TextBox)sender).Text.Trim();
        if (originalText.Length>0)
        {
            int inputOffset = e.Changes.ElementAt(0).Offset;
            char inputChar = originalText.ElementAt(inputOffset);
            if (!char.IsDigit(inputChar))
            {
                ((TextBox)sender).Text = originalText.Remove(inputOffset, 1);
            }
        }
    }

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

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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.

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Not sure if this is the correct way, but it works for me, running it on the TextChanged event TextBox has:

    private void CoordinateValidation(object sender, TextChangedEventArgs e) {
        TextBox inputBox = e.OriginalSource as TextBox;
        inputBox.TextChanged -= CoordinateValidation;
        int caretPos = inputBox.CaretIndex;
        foreach (TextChange change in e.Changes) {
            if (inputBox.Text.Substring(change.Offset, change.AddedLength).Any(c => !ValidChars.Contains(c)) ||
                inputBox.Text.Count(c => c == '.') > 1 ||
                (inputBox.Text.Length > 0 && inputBox.Text.Substring(1).Contains('-'))) {
                inputBox.Text = inputBox.Text.Remove(change.Offset, change.AddedLength);
                caretPos -= change.AddedLength;
            }
        }
        inputBox.CaretIndex = caretPos;
        inputBox.TextChanged += CoordinateValidation;
    }

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Have a look at the below code

private void txtbox1_KeyPress(object sender, KeyPressEventArgs e)
    {
        const char Delete = (char)8;
        e.Handled = !Char.IsDigit(e.KeyChar) && e.KeyChar != Delete;
    }

This will be helpful but users can Copy and Paste characters :-)