Question

我正在尝试弄清楚如何在发生验证错误时取消TextBox中的用户输入。如果用户尝试输入无效字符，我希望阻止将其添加到TextBox。

如何添加或修改以下代码以防止TextBox接受无效字符？是否可以不收听TextBox.TextChanged事件？

我的TextBox看起来像是：

<TextBox Validation.Error="OnSomeTextBoxValidationError">
    <TextBox.Text>
        <Binding Path="Value" NotifyOnValidationError="True" UpdateSourceTrigger="PropertyChanged">
            <Binding.ValidationRules>
                 <local:SomeValidationRule />
            </Binding.ValidationRules>
        </Binding>
    </TextBox.Text>
</TextBox>

我的自定义验证规则如下：

public class SomeValidationRule : ValidationRule
{
    public override ValidationResult Validate(object value, CultureInfo cultureInfo)
    {
        string hex_string = value as string;
        Match invalid_chars = Regex.Match(hex_string, "[^0-9a-fA-F]");
        bool is_valid = (invalid_chars.Success == false);
        string error_context = null;

        if (is_valid == false)
        {
            error_context = "Invalid characters";
        }

        return new ValidationResult(is_valid, error_context);
    }
}

我有一个错误处理程序...我能用它做什么吗？

private void OnSomeTextBoxValidationError(object sender, ValidationErrorEventArgs e)
{
    // Can I do anything here?
}

如果可能，请提供原始答案，而不是引用网址。我已经阅读了许多涉及事件处理程序的可能解决方案，但我没有遇到任何人讨论在ValidationRule中进行所有验证的可能性。

Answer 1

经过大量研究后，似乎完全控制TextBox输入的唯一方法是直接处理多个事件。根据C＃2008中的WPF食谱（第1版，第169页）：

不幸的是，没有简单的方法（目前）将有用的高级数据绑定功能与低级键盘处理相结合，这是防止用户完全键入无效字符所必需的。

以下是我创建的十六进制数字TextBox，它只接受字符a-f，A-F和0-9。

SomeClass.xaml

<TextBox
    x:Name="SomeTextBox"
    LostFocus="TextBoxLostFocus"
    PreviewKeyDown="TextBoxPreviewKeyDown"
    PreviewTextInput="TextBoxPreviewTextInput" />

SomeClass.xaml.cs

private string mInvalidCharPattern = "[^0-9a-fA-F]";

// In my case SomeClass derives from UserControl
public SomeClass()
{
    DataObject.AddPastingHandler(
        this.SomeTextBox,
        new DataObjectPastingEventHandler(TextBoxPasting));
}

private void TextBoxLostFocus(object sender, RoutedEventArgs e)
{
    // You may want to refresh the TextBox's Text here. If the user deletes
    // the contents of the TextBox and clicks off of it, then you can restore
    // the original value.
}

// Catch the space character, since it doesn't trigger PreviewTextInput
private void TextBoxPreviewKeyDown(object sender, KeyEventArgs e)
{
    if (e.Key == Key.Space) { e.Handled = true; }
}

// Do most validation here
private void TextBoxPreviewTextInput(object sender, TextCompositionEventArgs e)
{
    if (ValidateTextInput(e.Text) == false) { e.Handled = true; }
}

// Prevent pasting invalid characters
private void TextBoxPasting(object sender, DataObjectPastingEventArgs e)
{
    string lPastingText = e.DataObject.GetData(DataFormats.Text) as string;
    if (ValidateTextInput(lPastingText) == false) { e.CancelCommand(); }
}

// Do the validation in a separate function which can be reused
private bool ValidateTextInput(string aTextInput)
{
    if (aTextInput == null) { return false; }

    Match lInvalidMatch = Regex.Match(aTextInput, this.mInvalidCharPattern);
    return (lInvalidMatch.Success == false);
}

Answer 2

你可能已经看过这个，但这是最简单的解决方案，并且一直对我有用。我捕获了PreviewKeyDown事件和..

<TextBox PreviewKeyDown="TextBox_PreviewKeyDown" Width="150" Height="30"></TextBox>

private void TextBox_PreviewKeyDown(object sender, KeyEventArgs e)
{
    ... validation here, eg. to stop spacebar from being pressed, you'd use:

    if (e.Key == Key.Space) e.Handled = true;

}

Answer 3

我在Windows Phone Runtime 8.1应用程序中使用它只允许某些字符：

<TextBox x:Name="TextBoxTitle" 
                 MaxLength="24" 
                 InputScope="AlphanumericHalfWidth" 
                 TextChanged="TextBoxTitle_TextChanged"                      
                 KeyUp="TextBoxTitle_KeyUp"
                 Paste="TextBoxTitle_Paste"/>

using System.Text.RegularExpressions;

bool textBoxTitle_TextPasted = false;
private void TextBoxTitle_Paste(object sender, TextControlPasteEventArgs e)
{
    textBoxTitle_TextPasted = true;
}

// only allow characters A-Z, a-z, numbers and spaces
private void TextBoxTitle_TextChanged(object sender, TextChangedEventArgs e)
{
    string fileNameCompatibleString = Regex.Replace(TextBoxTitle.Text, "[^a-zA-Z0-9\x20]", String.Empty);
    if (TextBoxTitle.Text != fileNameCompatibleString)
    {
        if (textBoxTitle_TextPasted)
        {
            TextBoxTitle.Text = fileNameCompatibleString;
            TextBoxTitle.SelectionStart = fileNameCompatibleString.Length;
        }
        else
        {
            int selectionStartSaved = TextBoxTitle.SelectionStart;
            TextBoxTitle.Text = fileNameCompatibleString;
            TextBoxTitle.SelectionStart = selectionStartSaved-1;
        }               
    }
    textBoxTitle_TextPasted = false;
}

// close SIP keyboard on enter key up
private void TextBoxTitle_KeyUp(object sender, KeyRoutedEventArgs e)
{
    if (e.Key == Windows.System.VirtualKey.Enter)
    {
        Windows.ApplicationModel.Core.CoreApplication.GetCurrentView().CoreWindow.IsInputEnabled = false;
        Windows.ApplicationModel.Core.CoreApplication.GetCurrentView().CoreWindow.IsInputEnabled = true;
        e.Handled = true;
    }       
}

Answer 4

TextBox PreviewKeyUp

在TextBox PreviewKeyUp事件运行良好之后。通过将发件人转换为TextBox，在文本框中捕获当前文本。然后使用RegEx替换来替换无效字符。也可以在此处添加一些工具提示文本，但是现在这会删除无效字符并将背景变为红色，以立即获得用户反馈。

在WPF中取消验证错误时的TextBox输入

4 个答案:

SomeClass.xaml

SomeClass.xaml.cs