WPF验证之——必填验证

要事先必填验证，首先要重写ValidationRule类的Validate方法，然后在Binding中指定对应的ValidationRule。

第一步：重写ValidationRule的Validate

public class RequiredValidationRule:ValidationRule { public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo) { if (value == null || string.IsNullOrWhiteSpace(value.ToString())) { return new ValidationResult(false, "内容不能为空"); } return new ValidationResult(true, null); } }

第二步：窗体：

<TextBox Grid.Row="0" Grid.Column="1" Validation.ErrorTemplate="{StaticResource CT_TextBox_Required}" Style="{StaticResource Style_TextBox_Error}" <TextBox.Text> <Binding Path="Name" UpdateSourceTrigger="PropertyChanged"> <Binding.ValidationRules> <vr:RequiredValidationRule /> </Binding.ValidationRules> </Binding> </TextBox.Text> </TextBox>

第三步：错误控件的样式

<ControlTemplate x:Key="CT_TextBox_Required"> <DockPanel> <TextBlock Foreground="Red" FontSize="20" Text="!" /> <AdornedElementPlaceholder /> </DockPanel> </ControlTemplate> <Style x:Key="Style_TextBox_Error" TargetType="{x:Type TextBox}"> <Setter Property="Margin" Value="10,5,20,5" /> <Style.Triggers> <Trigger Property="Validation.HasError" Value="true"> <Setter Property="ToolTip" Value="{Binding RelativeSource={x:Static RelativeSource.Self},Path=(Validation.Errors)[0].ErrorContent}" /> </Trigger> </Style.Triggers> </Style>

我们来看看效果图：，貌似不错，但是还有不尽人意之处。在控件Focus时，控件内容为空，我希望此时就显示错误提示，而不是更改后再显示错误提示，首先要添加PreviewGotKeyboardFocus事件

private void TextBox_PreviewGotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e) { TextBox tb = sender as TextBox; tb.GetBindingExpression(TextBox.TextProperty).UpdateSource(); }

好，我们轻松地实现了必填验证。

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