使用 ValidationRule 类的 WPF 验证
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WPF validation using ValidationRule class
提问by Tech Jay
I am trying to add validation on a text for required field using the "ValidationRule" class. I have the following implementation of the class
我正在尝试使用“ValidationRule”类为必填字段的文本添加验证。我有以下类的实现
using System.Windows.Controls;
using System.Globalization;
public class RequiredField : ValidationRule
{
private String _errorMessage = String.Empty;
public string ErrorMessage
{
get { return _errorMessage; }
set { _errorMessage = value; }
}
public override ValidationResult Validate(object value, CultureInfo cultureInfo)
{
var str = value as string;
if (String.IsNullOrEmpty(str))
{
return new ValidationResult(true, this.ErrorMessage);
}
return new ValidationResult(true, null);
}
}
Further in my XAML, i have the following implementation of it:
进一步在我的 XAML 中，我有以下实现：
<TextBox Grid.Row="1" Grid.Column="3" Name="txtUserName" Height="23" VerticalAlignment="Top" Width="70" Grid.ColumnSpan="2" HorizontalAlignment="Left" MaxLength="50">
<TextBox.Text>
<Binding Path="Username" UpdateSourceTrigger="PropertyChanged">
<Binding.ValidationRules>
<validators:RequiredField ErrorMessage="username is required." />
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
and for displaying the error message, i have the following error template style in app.xaml
为了显示错误消息，我在 app.xaml 中有以下错误模板样式
<Style TargetType="{x:Type TextBox}">
<Setter Property="Validation.ErrorTemplate">
<Setter.Value>
<ControlTemplate>
<DockPanel LastChildFill="True">
<TextBlock DockPanel.Dock="Right"
Foreground="Orange"
Margin="5"
FontSize="12pt"
Text="{Binding ElementName=MyAdorner,
Path=AdornedElement.(Validation.Errors)[0].ErrorContent}">
</TextBlock>
<Border BorderBrush="Green" BorderThickness="3">
<AdornedElementPlaceholder Name="MyAdorner" />
</Border>
</DockPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="Validation.HasError" Value="true">
<Setter Property="ToolTip"
Value="{Binding RelativeSource={RelativeSource Self},
Path=(Validation.Errors)[0].ErrorContent}"/>
</Trigger>
</Style.Triggers>
</Style>
The code is compiling and running fine. Even the validationRule method is getting hit by the debugger. But the issue is that the message for error is not getting displayed.
该代码正在编译并运行良好。甚至validationRule 方法也被调试器击中。但问题是没有显示错误消息。
I have attached the Model using the following code :
我使用以下代码附加了模型：
ApplicationUsersUIContract ss = new ApplicationUsersUIContract();
this.DataContext = ss;
I am new to the concept of WPF. What am i missing here ? Any help is greatly appreciated.
我是 WPF 概念的新手。我在这里错过了什么？任何帮助是极大的赞赏。
采纳答案by Rohit Vats
Everything is perfect except you are passing isValidto trueeven in case of validation failure -
一切都很完美，除非您在验证失败的情况下传递isValid到true-
if (String.IsNullOrEmpty(str))
{
return new ValidationResult(true, this.ErrorMessage); <--- HERE
}
It should be false instead -
它应该是假的 -
return new ValidationResult(false, this.ErrorMessage);
