只允许在特定的文本字符

问题描述：

我怎么能只允许在Visual C＃文本框的某些字符？用户应当能够输入下列字符在文本框中，和其他一切应该阻止：0-9，+， - ，/，*，（，）

How can I only allow certain characters in a Visual C# textbox? Users should be able to input the following characters into a text box, and everything else should be blocked: 0-9, +, -, /, *, (, ).

我用谷歌来查找这个问题，但我得到的唯一的解决办法是只允许字母，数字只或禁止某些字符。我想是不是不允许某些字符，我希望禁止由不同的是，我把代码中的字符默认一切。

I've used Google to look up this problem, but the only solutions I'm getting are allowing only alphabetic characters, only numerical or disallowing certain characters. What I want is not disallowing certain characters, I want to disallow everything by default except the characters that I put in the code.

答

作为的评论中提到（和另一个答案，因为我输入），你需要注册一个事件处理程序来捕获上的文本框的keydown或按键事件。这是因为框TextChanged只发射时，文本框失去焦点

As mentioned in a comment (and another answer as I typed) you need to register an event handler to catch the keydown or keypress event on a text box. This is because TextChanged is only fired when the TextBox loses focus

下面的正则表达式可以让你搭配要允许这些字符

The below regex lets you match those characters you want to allow

Regex regex = new Regex(@"[0-9+\-\/\*\(\)]");
MatchCollection matches = regex.Matches(textValue);

和这样做是不允许的对面，抓住人物

and this does the opposite and catches characters that aren't allowed

Regex regex = new Regex(@"[^0-9^+^\-^\/^\*^\(^\)]");
MatchCollection matches = regex.Matches(textValue);

我不假定就会有一个匹配的人可以将文本粘贴到文本框中。在这种情况下捕捉框TextChanged

I'm not assuming there'll be a single match as someone could paste text into the textbox. in which case catch textchanged

textBox1.TextChanged += new TextChangedEventHandler(textBox1_TextChanged);
private void textBox1_TextChanged(object sender, EventArgs e)
{
    Regex regex = new Regex(@"[^0-9^+^\-^\/^\*^\(^\)]");
    MatchCollection matches = regex.Matches(textBox1.Text);
    if (matches.Count > 0) {
       //tell the user
    }
}

和验证单一按键

textBox1.KeyPress += new KeyPressEventHandler(textBox1_KeyPress);
private void textBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
    // Check for a naughty character in the KeyDown event.
    if (System.Text.RegularExpressions.Regex.IsMatch(e.KeyChar.ToString(), @"[^0-9^+^\-^\/^\*^\(^\)]"))
    {
        // Stop the character from being entered into the control since it is illegal.
        e.Handled = true;
    }
}

只允许在特定的文本字符

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