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

http://blog.csdn.net/The_Eyes/article/details/61415096