设置DataContext之后的DataTemplate选择器 [英] DataTemplate Selector after DataContext Set
问题描述
我有2列的DataGrid。基于绑定到ParameterDataType的第一列，我想在第二列中加载适当的模板。
I have a DataGrid with 2 columns. Based on the first column which is bound to ParameterDataType I want to load the appropriate template in the second column.
此代码的问题是在加载DataGrid之前，模板选择器正在执行，因此该项目为null。设置ControlTemplate的DataContext之后，是否可以执行模板选择器。请帮忙。
Problem with this code is before the DataGrid has been loaded, the template selector is executing as a result the item is null. Is there a way to execute the Template Selector after the ControlTemplate's DataContext is set. Please help.
这是我的xaml：
<uwpControls:DataGrid Grid.Row="4"
ItemsSource="{x:Bind ViewModel.ServiceMethodsData,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
AutoGenerateColumns="False">
<uwpControls:DataGrid.Resources>
<DataTemplate x:Key="StringTemplate">
<TextBox Width="150" Height="30" VerticalAlignment="Center"></TextBox>
</DataTemplate>
<DataTemplate x:Key="IntegerTemplate">
<controls:TextBoxNumeric Width="150" Height="30" VerticalAlignment="Center"></controls:TextBoxNumeric>
</DataTemplate>
<DataTemplate x:Key="BooleanTemplate">
<CheckBox IsChecked="False"></CheckBox>
</DataTemplate>
<local:MethodValueDataTemplateSelector x:Key="MethodValueTemplateSelector"
StringTemplate="{StaticResource StringTemplate}"
IntegerTemplate="{StaticResource IntegerTemplate}"
BooleanTemplate="{StaticResource BooleanTemplate}"/>
</uwpControls:DataGrid.Resources>
<uwpControls:DataGrid.Columns>
<uwpControls:DataGridTextColumn Header="First Column"
Binding="{Binding ParameterDataType, Mode=OneWay}"/>
<uwpControls:DataGridTemplateColumn Header="Second Column">
<uwpControls:DataGridTemplateColumn.CellTemplate>
<DataTemplate>
<ContentControl x:Name="MethodValueContentControl"
Content="{Binding Path=.}"
ContentTemplateSelector="{StaticResource MethodValueTemplateSelector}"></ContentControl>
</DataTemplate>
</uwpControls:DataGridTemplateColumn.CellTemplate>
</uwpControls:DataGridTemplateColumn>
</uwpControls:DataGrid.Columns>
</uwpControls:DataGrid>
这是我的DataTemplate选择器
Here is my DataTemplate selector
public class MethodValueDataTemplateSelector : DataTemplateSelector
{
public DataTemplate StringTemplate { get; set; }
public DataTemplate IntegerTemplate { get; set; }
public DataTemplate BooleanTemplate { get; set; }
protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
{
//I want to do something like if(DataContext.ParameterDataType=="Int") return IntegerTemplate etc
return StringTemplate;
}
}
这是我的ViewModel
Here is my ViewModel
public class ServiceUtilityMethodsViewModel
{
private ObservableCollection<VmServiceMethodsViewDataGridModel> _serviceMethodsData;
public ObservableCollection<VmServiceMethodsViewDataGridModel> ServiceMethodsData
{
get => _serviceMethodsData;
set => Set(ref _serviceMethodsData, value);
}
public ServiceUtilityMethodsViewModel(INavigationService navigationService) : base(navigationService)
{
PopulateServiceData();
}
private void PopulateServiceData()
{
ServiceMethodsData = new ObservableCollection<VmServiceMethodsViewDataGridModel>();
ServiceMethodsData.Add(new VmServiceMethodsViewDataGridModel()
{
ParameterName = "Param1",
ParameterDataType = "String"
});
ServiceMethodsData.Add(new VmServiceMethodsViewDataGridModel()
{
ParameterName = "Param2",
ParameterDataType = "Int"
});
ServiceMethodsData.Add(new VmServiceMethodsViewDataGridModel()
{
ParameterName = "Param3",
ParameterDataType = "bool"
});
}
}
}
这是我的模型课程
public class VmServiceMethodsViewDataGridModel : BindableBaseThreadSafe
{
private string _parameterName;
private string _parameterDataType;
public string ParameterName
{
get => _parameterName;
set => Set(ref _parameterName, value);
}
public string ParameterDataType //I want the template selector to work based on this column.
{
get => _parameterDataType;
set => Set(ref _parameterDataType, value);
}
}
推荐答案
您应该将 DataTemplateSelector 分配给 DataGridTemplateColumn.CellTemplateSelector 和 DataGridTemplateColumn.CellEditingTemplateSelector 直接。
You should assign the DataTemplateSelector to DataGridTemplateColumn.CellTemplateSelector and DataGridTemplateColumn.CellEditingTemplateSelector directly.
我没有检查UWP版本。我认为UWP DataGridTemplateColumn 没有此模板选择器属性。在这种情况下，您可以坚持使用当前的XAML，但也不要忘记定义 CellEditingTemplate （例如，替换 TextBlock 带有 TextBox 的 CellEditingTemplate 版本-最好使用 TextBlock 在您的默认 CellTemplate 中，因为它看起来更好）。在UWP版本中肯定会存在属性 CellTemplate 和 CellEditingTemplate 。
I didn't check the UWP version. I think the UWP DataGridTemplateColumn doesn't have this template selector properties. In this case you can stick to your current XAML, but don't forget to define a CellEditingTemplate too (e.g., replace the TextBlock with a TextBox for the CellEditingTemplate version - better use a TextBlock in your default CellTemplate as it looks better). The properties CellTemplate and CellEditingTemplate exist for sure in the UWP version.
XAML DataGrid 定义
XAML DataGrid definition
<uwpControls:DataGrid ItemsSource="{x:Bind ViewModel.ServiceMethodsData,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"
AutoGenerateColumns="False">
<uwpControls:DataGrid.Resources>
<DataTemplate x:Key="StringTemplate">
<TextBox Width="150" Height="30" VerticalAlignment="Center" />
</DataTemplate>
<DataTemplate x:Key="IntegerTemplate">
<controls:TextBoxNumeric Width="150" Height="30" VerticalAlignment="Center" />
</DataTemplate>
<DataTemplate x:Key="BooleanTemplate">
<CheckBox IsChecked="False" />
</DataTemplate>
<local:MethodValueDataTemplateSelector x:Key="MethodValueTemplateSelector"
StringTemplate="{StaticResource StringTemplate}"
IntegerTemplate="{StaticResource IntegerTemplate}"
BooleanTemplate="{StaticResource BooleanTemplate}" />
</uwpControls:DataGrid.Resources>
<uwpControls:DataGrid.Columns>
<uwpControls:DataGridTextColumn Header="First Column"
Binding="{Binding ParameterDataType, Mode=OneWay}" />
<uwpControls:DataGridTemplateColumn Header="Second Column"
CellTemplateSelector="{StaticResource MethodValueTemplateSelector}"
CellEditingTemplateSelector="{StaticResource MethodValueTemplateSelector}">
</uwpControls:DataGridTemplateColumn>
</uwpControls:DataGrid.Columns>
</uwpControls:DataGrid>
DataTemplateSelector 也非常简单。 br>
SelectTemplateCore 覆盖的参数是项目和项目的容器（这是 FrameWorkElement 和 ContentControl 大部分时间）。
该项目始终是数据模型，而 DataContext 。在您的情况下，该项目的类型为 VmServiceMethodsViewDataGridModel 。
The DataTemplateSelector is also quite simple.
The parameters of the SelectTemplateCore override are the item and the item's container (which is a FrameWorkElement and a ContentControl most of the time).
The item is always the data model and the DataContext of the current row. In your case the item is of type VmServiceMethodsViewDataGridModel.
容器是 FrameWorkElement ，用于包装模型以进行渲染，例如 ListBoxItem 。在您的情况下，容器的类型应为 DataGridRow 。
The container is the FrameWorkElement that wraps the model for rendering e.g. ListBoxItem. In your case the container should be of type DataGridRow.
只需将item参数转换为适当的类型并求值
Simply cast the item parameter to the appropriate type and evaluate it.
MethodValueDataTemplateSelector.cs
public class MethodValueDataTemplateSelector : DataTemplateSelector
{
public DataTemplate StringTemplate { get; set; }
public DataTemplate IntegerTemplate { get; set; }
public DataTemplate BooleanTemplate { get; set; }
protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
{
// Return if the control is not loaded yet and the item is therefore null
// or the item is of the wrong type
if (!(item is VmServiceMethodsViewDataGridModel dataModel))
{
return null;
}
// I want to do something like:
// if(DataContext.ParameterDataType=="Int") return IntegerTemplate etc
switch (dataModel.ParameterDataType)
{
case string value when value.Equals("Int", StringComparison.OrdinalIgnoreCase):
return IntegerTemplate;
case string value when value.Equals("String", StringComparison.OrdinalIgnoreCase):
return StringTemplate;
case string value when value.Equals("Bool", StringComparison.OrdinalIgnoreCase):
return BooleanTemplate;
default:
return null;
}
}
}
这篇关于设置DataContext之后的DataTemplate选择器的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
