我第一次尝试在 XAML / WPF 中实现数据验证。我读过一些教程,似乎有很多种方法可以做到这一点。我已经选择了一种方法,但它不起作用。
首先,理想情况下,这就是我希望显示错误的方式(
上方和
ComboBox
的右)。如果可以的话...
我创建了一个
Label
:
ValidationRule
然后,我将其添加到 XAML 中的
using System;
using System.Globalization;
using System.Windows.Controls;
namespace OCLMEditor.ValidationRules
{
class StudyPointValidationRule : ValidationRule
{
public bool BibleReading { get; set; }
public StudyPointValidationRule()
{
BibleReading = false;
}
public override ValidationResult Validate(object value, CultureInfo cultureInfo)
{
if(value == null)
return new ValidationResult(false, "The study point has not been set.");
int iStudy = (int)value;
if(BibleReading)
{
if(iStudy > 17)
return new ValidationResult(false, "Maximum study point for bible readings is 17.");
}
else
{
if(iStudy == 7 || iStudy > 51)
return new ValidationResult(false, "Study points 7, 52 and 53 are not permitted for student items.");
}
return new ValidationResult(true, null);
}
}
}
类中:
Window
在
xmlns:ValidationRules="clr-namespace:OCLMEditor.ValidationRules":
:
Window.Resources
然后,对于我想要应用此验证的第一个组合框,我将其更改为:
<ControlTemplate x:Key="StudyPointValidationTemplate">
<DockPanel>
<TextBlock Foreground="Red" FontSize="20">!</TextBlock>
<AdornedElementPlaceholder/>
</DockPanel>
</ControlTemplate>
致:
<ComboBox DataContext="{Binding DataContext, ElementName=oclmEditor}"
ItemsSource="{Binding ReadingStudyPointsList}"
ItemContainerStyle="{StaticResource StudyPointComboBoxStyle}"
ItemTemplate="{StaticResource StudyPointComboItem}"
Validation.ErrorTemplate="{StaticResource StudyPointValidationTemplate}"
Tag="{Binding Meeting.BibleReadingMainName, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"
SelectedValue="{Binding Meeting.BibleReadingMainStudyPoint, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
SelectedValuePath="Number"/>
我收到此错误:
System.Windows.Data 错误:40:BindingExpression 路径错误:在“对象”“OCLMEditorViewModel”(HashCode=17586541) 上找不到“Number”属性。绑定表达式:路径=数字; DataItem='OCLMEditorViewModel'(哈希码=17586541);目标元素是“ComboBox”(名称=“”);目标属性是“SelectedValuePath”(类型“String”)
我不明白为什么,因为我以前可以使用“数字”。
我已经扩展了模型数据类,以便在值太高时抛出异常。例如:
<ComboBox DataContext="{Binding DataContext, ElementName=oclmEditor}"
ItemsSource="{Binding ReadingStudyPointsList}"
ItemContainerStyle="{StaticResource StudyPointComboBoxStyle}"
ItemTemplate="{StaticResource StudyPointComboItem}"
Validation.ErrorTemplate="{StaticResource StudyPointValidationTemplate}"
Tag="{Binding Meeting.BibleReadingMainName, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"
SelectedValue="{Binding Meeting.BibleReadingMainStudyPoint, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
>
<ComboBox.SelectedValuePath>
<Binding Path="Number">
<Binding.ValidationRules>
<ValidationRules:StudyPointValidationRule BibleReading="True"/>
</Binding.ValidationRules>
</Binding>
</ComboBox.SelectedValuePath>
</ComboBox>
我肯定会抛出异常:
参数名称:圣经阅读学习点数上限为17。 位于 D:\My Programs\OCLMEditor\OCLMEditor\Data\MeetingInfo\Meeting.cs 中的 OCLMEditor.Data.MeetingInfo.Meeting.set_BibleReadingMainStudyPoint(Int32 值):第 234 行 在 D:\My Programs\OCLMEditor\OCLMEditor\ViewModels\OCLMEditorViewModel.cs 中的 OCLMEditor.OCLMEditorViewModel.set_SelectedStudentItem(学生值):第 184 行
我更改了 XAMl,因为 ValidationRule 在此实例中不适用:
[XmlIgnore]
public int BibleReadingMainStudyPoint
{
get { return _TFGW.BibleReadingItem.Main.StudyPoint; }
set
{
if (value > 17)
throw new ArgumentOutOfRangeException("Maximum Bible reading study point is 17.");
_TFGW.BibleReadingItem.Main.StudyPoint = value;
MarkDirty();
OnPropertyChanged("BibleReadingMainStudyPoint");
}
}
所以我希望它现在能够直观地显示错误。屏幕上没有任何内容。
资源:
<Binding.ValidationRules>
<ExceptionValidationRule/>
</Binding.ValidationRules>
我可以看出屏幕上有一个验证符号。但它并没有减少组合的宽度,所以可以看到。
<Window.Resources>
<ValueConverters:StudyPointWorkingOn x:Key="StudyPointWorkingOn" />
<Style x:Key="StudyPointComboBoxStyle" TargetType="ComboBoxItem">
<Setter Property="Tag" Value="{Binding Number}" />
<Style.Triggers>
<DataTrigger Value="True">
<DataTrigger.Binding>
<MultiBinding Converter="{StaticResource StudyPointWorkingOn}">
<Binding RelativeSource="{RelativeSource Self}" Path="Tag"/>
<Binding Path="DataContext" ElementName="oclmEditor" UpdateSourceTrigger="PropertyChanged" />
<Binding Path="Tag" RelativeSource="{RelativeSource AncestorType=ComboBox}"/>
</MultiBinding>
</DataTrigger.Binding>
<Setter Property="Background" Value="Red"/>
</DataTrigger>
</Style.Triggers>
</Style>
<DataTemplate x:Key="StudyPointComboItem">
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Number}"/>
<TextBlock Text=" - "/>
<TextBlock Text="{Binding Title}"/>
</StackPanel>
</DataTemplate>
<ControlTemplate x:Key="StudyPointValidationTemplate">
<DockPanel>
<TextBlock Foreground="Red" FontSize="20">!</TextBlock>
<AdornedElementPlaceholder/>
</DockPanel>
</ControlTemplate>
</Window.Resources>
是一个字符串。它告诉 SelectedValuePath
将所选数据项的哪个值分配给 ComboBox
属性。对此没有什么可以验证的;这不是告诉您用户选择了什么的属性。当选择更改时,它不应该更改,因为 SelectedValue
始终是您想要用于 Number
的属性(除非您更改 SelectedValue
中项目的类型 - 但这不是您正在做的事情)。
您想要与验证绑定的属性是
ComboBox
,您已将其作为问题中的属性。
SelectedValue
如果你想实现验证,你应该这样做:
<ComboBox
...other properties...
SelectedValuePath="Number"
>
<ComboBox.SelectedValue>
<Binding
Path="Meeting.BibleReadingMainStudyPoint"
Mode="TwoWay"
UpdateSourceTrigger="PropertyChanged"
>
<Binding.ValidationRules>
<ValidationRules:StudyPointValidationRule BibleReading="True"/>
</Binding.ValidationRules>
</Binding>
</ComboBox.SelectedValue>
<ComboBox.Style>
<Style
TargetType="ComboBox"
BasedOn="{StaticResource {x:Type ComboBox}}"
>
<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>
</ComboBox.Style>
</ComboBox>
使用
<ComboBox SelectedValuePath="Number" DataContext="{Binding DataContext, ElementName=oclmEditor}"
ItemsSource="{Binding ReadingStudyPointsList}"
ItemContainerStyle="{StaticResource StudyPointComboBoxStyle}"
ItemTemplate="{StaticResource StudyPointComboItem}"
Validation.ErrorTemplate="{StaticResource StudyPointValidationTemplate}"
Tag="{Binding Meeting.BibleReadingMainName, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}"
SelectedValue="{Binding Meeting.BibleReadingMainStudyPoint, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
>
<ComboBox.SelectedValue>
<Binding Path="Meeting.BibleReadingMainName" UpdateSourceTrigger="PropertyChanged" Mode="TwoWay">
<Binding.ValidationRules>
<ValidationRules:StudyPointValidationRule BibleReading="True"/>
</Binding.ValidationRules>
</Binding>
</ComboBox.SelectedValue>
</ComboBox>
只是为了告诉使用哪个属性从 SelectedValuePath
获取 SelectedValue
。