不要忘记用户可以在文本框中粘贴无效文本。

如果你想限制它，遵循下面的代码:

private void ultraTextEditor1_TextChanged(object sender, EventArgs e)
{
    string append="";
    foreach (char c in ultraTextEditor1.Text)
    {
        if ((!Char.IsNumber(c)) && (c != Convert.ToChar(Keys.Back)))
        {

        }
        else
        {
            append += c;
        }
    }

    ultraTextEditor1.Text = append;
}   

两个选择:

Use a NumericUpDown instead. NumericUpDown does the filtering for you, which is nice. Of course it also gives your users the ability to hit the up and down arrows on the keyboard to increment and decrement the current value. Handle the appropriate keyboard events to prevent anything but numeric input. I've had success with this two event handlers on a standard TextBox: private void textBox1_KeyPress(object sender, KeyPressEventArgs e) { if (!char.IsControl(e.KeyChar) && !char.IsDigit(e.KeyChar) && (e.KeyChar != '.')) { e.Handled = true; } // only allow one decimal point if ((e.KeyChar == '.') && ((sender as TextBox).Text.IndexOf('.') > -1)) { e.Handled = true; } }

您可以删除'的支票。如果你的文本框不允许小数点，'(和后续检查不止一个'.')。你也可以添加一个检查'-'如果你的文本框应该允许负值。

如果您想限制用户的位数，请使用:textBox1。MaxLength = 2;//这将允许用户只输入2位数字

我已经为各种验证创建了一个可重用的文本框扩展类，并考虑共享它。

您所需要做的就是引发一个TextChange事件，然后调用Validate方法。它是这样的:

private void tbxAmount_TextChanged(object sender, EventArgs e)
{ 
    tbxAmount.Validate(TextValidator.ValidationType.Amount);
}

下面是扩展类:

public static class TextValidator
{
    public enum ValidationType
    {
        Amount,
        Integer
    }

    /// <summary>
    /// Validate a textbox on text change.
    /// </summary>
    /// <param name="tbx"></param>
    /// <param name="validationType"></param>
    public static void Validate(this TextBox tbx, ValidationType validationType)
    {
        PerformValidation(tbx, validationType);
        tbx.Select(tbx.Text.Length, 0);
    }


    private static void PerformValidation(this TextBox tbx, ValidationType validationType)
    {
        char[] enteredString = tbx.Text.ToCharArray();
        switch (validationType)
        {
            case ValidationType.Amount:
                tbx.Text = AmountValidation(enteredString);
                break;

            case ValidationType.Integer:
                tbx.Text = IntegerValidation(enteredString);
                break;

            default:
                break;
        }

        tbx.SelectionStart = tbx.Text.Length;
    }



    private static string AmountValidation(char[] enteredString)
    {
        string actualString = string.Empty;
        int count = 0;
        foreach (char c in enteredString.AsEnumerable())
        {
            if (count >= 1 && c == '.')
            { actualString.Replace(c, ' '); actualString.Trim(); }
            else
            {
                if (Char.IsDigit(c))
                {
                    actualString = actualString + c;
                }

                if (c == '.')
                {
                    actualString = actualString + c; count++;
                }

                else
                {
                    actualString.Replace(c, ' ');
                    actualString.Trim();
                }
            }
        }
        return actualString;
    }


    private static string IntegerValidation(char[] enteredString)
    {
        string actualString = string.Empty;
        foreach (char c in enteredString.AsEnumerable())
        {
            if (Char.IsDigit(c))
            {
                actualString = actualString + c;
            }
            else
            {
                actualString.Replace(c, ' ');
                actualString.Trim();
            }
        }
        return actualString;
    }
}

你可以在这里找到完整的代码

这是一个简单的独立的Winforms自定义控件，从标准的TextBox派生而来，只允许System。Int32输入(它可以很容易地适用于其他类型，如System。Int64,等等)。它支持复制/粘贴操作和负数:

public class Int32TextBox : TextBox
{
    protected override void OnKeyPress(KeyPressEventArgs e)
    {
        base.OnKeyPress(e);

        NumberFormatInfo fi = CultureInfo.CurrentCulture.NumberFormat;

        string c = e.KeyChar.ToString();
        if (char.IsDigit(c, 0))
            return;

        if ((SelectionStart == 0) && (c.Equals(fi.NegativeSign)))
            return;

        // copy/paste
        if ((((int)e.KeyChar == 22) || ((int)e.KeyChar == 3))
            && ((ModifierKeys & Keys.Control) == Keys.Control))
            return;

        if (e.KeyChar == '\b')
            return;

        e.Handled = true;
    }

    protected override void WndProc(ref System.Windows.Forms.Message m)
    {
        const int WM_PASTE = 0x0302;
        if (m.Msg == WM_PASTE)
        {
            string text = Clipboard.GetText();
            if (string.IsNullOrEmpty(text))
                return;

            if ((text.IndexOf('+') >= 0) && (SelectionStart != 0))
                return;

            int i;
            if (!int.TryParse(text, out i)) // change this for other integer types
                return;

            if ((i < 0) && (SelectionStart != 0))
                return;
        }
        base.WndProc(ref m);
    }

2017年更新:我的第一个答案有一些问题:

你可以输入一个比给定类型的整数更长的值(例如2147483648大于Int32.MaxValue); 更一般地说，对于输入的结果没有真正的验证; 它只处理int32，你必须写特定的TextBox衍生控件为每种类型(Int64等)

所以我提出了另一个更通用的版本，它仍然支持复制/粘贴，+和-号等。

public class ValidatingTextBox : TextBox
{
    private string _validText;
    private int _selectionStart;
    private int _selectionEnd;
    private bool _dontProcessMessages;

    public event EventHandler<TextValidatingEventArgs> TextValidating;

    protected virtual void OnTextValidating(object sender, TextValidatingEventArgs e) => TextValidating?.Invoke(sender, e);

    protected override void WndProc(ref Message m)
    {
        base.WndProc(ref m);
        if (_dontProcessMessages)
            return;

        const int WM_KEYDOWN = 0x100;
        const int WM_ENTERIDLE = 0x121;
        const int VK_DELETE = 0x2e;

        bool delete = m.Msg == WM_KEYDOWN && (int)m.WParam == VK_DELETE;
        if ((m.Msg == WM_KEYDOWN && !delete) || m.Msg == WM_ENTERIDLE)
        {
            DontProcessMessage(() =>
            {
                _validText = Text;
                _selectionStart = SelectionStart;
                _selectionEnd = SelectionLength;
            });
        }

        const int WM_CHAR = 0x102;
        const int WM_PASTE = 0x302;
        if (m.Msg == WM_CHAR || m.Msg == WM_PASTE || delete)
        {
            string newText = null;
            DontProcessMessage(() =>
            {
                newText = Text;
            });

            var e = new TextValidatingEventArgs(newText);
            OnTextValidating(this, e);
            if (e.Cancel)
            {
                DontProcessMessage(() =>
                {
                    Text = _validText;
                    SelectionStart = _selectionStart;
                    SelectionLength = _selectionEnd;
                });
            }
        }
    }

    private void DontProcessMessage(Action action)
    {
        _dontProcessMessages = true;
        try
        {
            action();
        }
        finally
        {
            _dontProcessMessages = false;
        }
    }
}

public class TextValidatingEventArgs : CancelEventArgs
{
    public TextValidatingEventArgs(string newText) => NewText = newText;
    public string NewText { get; }
}

对于Int32，你可以从它导出，像这样:

public class Int32TextBox : ValidatingTextBox
{
    protected override void OnTextValidating(object sender, TextValidatingEventArgs e)
    {
        e.Cancel = !int.TryParse(e.NewText, out int i);
    }
}

或w/o派生，使用新的textvalididating事件，像这样:

var vtb = new ValidatingTextBox();
...
vtb.TextValidating += (sender, e) => e.Cancel = !int.TryParse(e.NewText, out int i);

但它的优点是它适用于任何字符串和任何验证例程。

这里有30多个答案，很多答案都是有用的。但我想分享system。windows。forms。textbox和system。windows。controls。textbox的通用形式。

在System.Windows.Controls.TextBox中没有可用的按键事件。 这个答案是为那些想用同样的逻辑实现System.Windows.Forms.TextBox和System.Windows.Controls.TextBox的人准备的。

这是NumberTextBox代码。对于System.Windows.Controls.TextBox，使用注释行代替之前的行。

public class NumberTextBox : System.Windows.Forms.TextBox
//public class NumberTextBox : System.Windows.Controls.TextBox
{
    private double _maxValue;
    private double _minValue;
    private bool _flag;
    private string _previousValue;

    public NumberTextBox()
    {
        this.TextAlign = HorizontalAlignment.Right;
        //TextAlignment = TextAlignment.Right;
        KeyDown += TextBox_KeyDown;
        TextChanged += TextBox_TextChanged;
        _minValue = double.MinValue;
        _maxValue = double.MaxValue;
    }

    private void TextBox_KeyDown(object sender, KeyEventArgs e)
    {
        _previousValue = this.Text;
        _flag = this.SelectedText.Length > 0;
    }

    private void TextBox_TextChanged(object sender, EventArgs e)
    //private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
    {
        var text = this.Text;
        if (text.Length < 1) return;
        var cursorPosition = SelectionStart == 0 ? SelectionStart : SelectionStart - 1;
        var insertedChar = text[cursorPosition];
        if (IsInvalidInput(insertedChar, cursorPosition, text))
        {
            HandleText(text, cursorPosition);
        }
        ValidateRange(text, cursorPosition);
    }

    private bool IsInvalidInput(char insertedChar, int cursorPosition, string text)
    {
        return !char.IsDigit(insertedChar) && insertedChar != '.' && insertedChar != '-' ||
               insertedChar == '-' && cursorPosition != 0 ||
               text.Count(x => x == '.') > 1 ||
               text.Count(x => x == '-') > 1;
    }

    private void HandleText(string text, int cursorPosition)
    {
        this.Text = _flag ? _previousValue : text.Remove(cursorPosition, 1);
        this.SelectionStart = cursorPosition;
        this.SelectionLength = 0;
    }

    private void ValidateRange(string text, int cursorPosition)
    {
        try
        {
            if (text == "." || _minValue < 0 && text == "-") return;
            var doubleValue = Convert.ToDouble(text);
            if (doubleValue > _maxValue || doubleValue < _minValue)
            {
                HandleText(text, cursorPosition);
            }
        }
        catch (Exception)
        {
            HandleText(text, cursorPosition);
        }
    }

    protected void SetProperties(double minValue = double.MinValue, double maxValue = double.MaxValue)
    {
        _minValue = minValue;
        _maxValue = maxValue;
    }       

}

PositiveNumberTextBox代码:

public class PositiveNumberTextBox : NumberTextBox
{
    public PositiveNumberTextBox()
    {
        SetProperties(0);
    }
}

FractionNumberTextBox代码:

public class FractionNumberTextBox : NumberTextBox
{
    public FractionNumberTextBox()
    {
        SetProperties(0, 0.999999);
    }
}

private void txt3_KeyPress(object sender, KeyPressEventArgs e)
{
    for (int h = 58; h <= 127; h++)
    {
        if (e.KeyChar == h)             //58 to 127 is alphabets tat will be         blocked
        {
            e.Handled = true;
        }
    }
    for(int k=32;k<=47;k++)
    {
        if (e.KeyChar == k)              //32 to 47 are special characters tat will 
        {                                  be blocked
            e.Handled = true;
        }
    }
}

试试这个很简单