wpf 限制文本框只允许十进制数字

Restrict textbox to allow only decimal numbers

提问by Mussammil

I have a requirement to make a decimal textbox (Money textbox) which:

我需要制作一个十进制文本框（Money 文本框），它：

1. only allows numbers 0-9 (allow upper numpad keys 0-9 and right numpad keys 0-9);
2. allows only one dot which don't appear on start.

1. 只允许数字 0-9（允许上小键盘键 0-9 和右小键盘键 0-9）；
2. 只允许一个不在开始时出现的点。

Valid:

有效的：

• 0.5
• 1
• 1.5000

• 0.5
• 1
• 1.5000

Invalid:

无效的：

• .5
• 5.500.55

• .5
• 5.500.55

Edit

编辑

my code is :

我的代码是：

 private void floatTextBox_PreviewTextInput(object sender, TextCompositionEventArgs e)
    {
        e.Handled = !TextBoxValidation.AreAllValidDecimalChars(e.Text);
    }


  public static class TextBoxValidation
{
    public static bool AreAllValidDecimalChars(string str)
    {
        bool ret = false;
        int x = 0;
        foreach (char c in str)
        {
            x = (int)c;
        }
        if (x >= 48 && x <= 57 || x == 46)
        {
            ret = true;
        }
        return ret;
    }
}

回答by Bas

If you want to allow copy and pasting as well you cannot do it with keyboard events. A TextBoxhas a TextChangedevent which allows you to handle this event appropirately. If you want to block any input that is not a number or dot you could handle it like this:

如果您还想允许复制和粘贴，则不能使用键盘事件来实现。ATextBox有一个TextChanged事件，它允许您适当地处理此事件。如果你想阻止任何不是数字或点的输入，你可以这样处理：

private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
    //get the textbox that fired the event
    var textBox = sender as TextBox;
    if (textBox == null) return;

    var text = textBox.Text;
    var output = new StringBuilder();
    //use this boolean to determine if the dot already exists
    //in the text so far.
    var dotEncountered = false;
    //loop through all of the text
    for (int i = 0; i < text.Length; i++)
    {
        var c = text[i];
        if (char.IsDigit(c))
        {
            //append any digit.
            output.Append(c);
        }
        else if (!dotEncountered && c == '.') 
        {
            //append the first dot encountered
            output.Append(c);
            dotEncountered = true;
        }
    }
    var newText = output.ToString();
    textBox.Text = newText;
    //set the caret to the end of text
    textBox.CaretIndex = newText.Length;
}

回答by Sheridan

You can achieve your goal by simply implementing two event handlers on a TextBox:

您可以通过简单地在 a 上实现两个事件处理程序来实现您的目标TextBox：

TextCompositionEventHandler textBox_PreviewTextInput = 
    new TextCompositionEventHandler((s, e) => e.Handled = !e.Text.All(
    c => Char.IsNumber(c) || c == '.'));
KeyEventHandler textBox_PreviewKeyDown = new KeyEventHandler(
    (s, e) => e.Handled = e.Key == Key.Space);

textBox.PreviewTextInput += textBox_PreviewTextInput;
textBox.PreviewKeyDown += textBox_PreviewKeyDown;