使用 MVVM 上下文菜单项命令绑定 WPF
我知道这个问题已经在许多网站和 StackOverFlow 中以不同的方式被问过很多次,但我找到的所有答案都没有帮助我,准确地说,我无法理解它们并在我的应用程序中实现。所以我想从我的应用程序中添加一些代码,以便你们可以更好地帮助我。
问题陈述:我正在使用 WPF DataGrid。我添加了一个上下文菜单,并且有 3 个选项“剪切”、“复制”、“粘贴”。我正在使用 MVVM 进行开发。我想将这些选项数据绑定到我的 ViewModel 中的命令。但我却无法做到同样的事情。上下文菜单选项根本没有绑定数据!
这是我在 XAML 中的网格代码:
<custom:DataGrid
x:Name="DataGrid_Standard"
Grid.Row="1" Grid.Column="1"
AutoGenerateColumns="False"
IsSynchronizedWithCurrentItem="True"
Background="Transparent"
ItemsSource="{Binding FullGridData}"
ItemContainerStyle="{StaticResource defaultRowStyle}"
ColumnHeaderStyle="{StaticResource DefaultColumnHeaderStyle}"
Grid.ColumnSpan="2">
然后我有一个 ContextMenu 和一个标题元素样式
<ContextMenu x:Key="columnHeaderMenu">
<MenuItem Command="{Binding CutCommand}"
Header="Test" />
<MenuItem Header="Copy"/>
<MenuItem Header="Paste"/>
</ContextMenu>
<Style TargetType="{x:Type custom:DataGridColumnHeader}" x:Key="DefaultColumnHeaderStyle">
<Setter Property="ContextMenu" Value="{DynamicResource columnHeaderMenu}" >
</Style>
此行位于我的构造函数中
public Window1()
{
this.DataContext = new AppData();
}
此代码位于我的 AppData 类中:
public class AppData
{
private IList<GridData> fullGridData = new ObservableCollection<GridData>();<br>
public IList<GridData> FullGridData
{
get { return fullGridData; }
set { fullGridData = value; }
}
private DelegateCommand<object> cutCommand;
public DelegateCommand<object> CutCommand
{
get
{
if (cutCommand == null)
{
cutCommand = new DelegateCommand<object>(CutColumn);
}
return cutCommand;
}
}
private void CutColumn(object obj)
{
//some code goes here
}
}
** 我想确切地知道我在哪里做错了?为什么数据绑定没有发生? 请帮助我解决这个问题。请向我提供示例代码或对我当前代码的修改,我可以从中实现它。 **
I know this question has been asked many times in different ways in many websites and also in StackOverFlow but all the answers I found are not helping me ot to be precise I am not able to understand them and implement in my application. So I thought of putting some code from my application so that you people can help me better.
Problem Statement : I am using a WPF DataGrid. I have added a Context Menu and I have 3 options Cut,Copy,Paste. I am using MVVM for development. I want to DataBind these options to Commands in my ViewModel. But I am unable to do the same. The context menu options are not getting data bound at all !!!
This is my Grid Code in XAML :
<custom:DataGrid
x:Name="DataGrid_Standard"
Grid.Row="1" Grid.Column="1"
AutoGenerateColumns="False"
IsSynchronizedWithCurrentItem="True"
Background="Transparent"
ItemsSource="{Binding FullGridData}"
ItemContainerStyle="{StaticResource defaultRowStyle}"
ColumnHeaderStyle="{StaticResource DefaultColumnHeaderStyle}"
Grid.ColumnSpan="2">
Then I have a ContextMenu and a Style for Header Element
<ContextMenu x:Key="columnHeaderMenu">
<MenuItem Command="{Binding CutCommand}"
Header="Test" />
<MenuItem Header="Copy"/>
<MenuItem Header="Paste"/>
</ContextMenu>
<Style TargetType="{x:Type custom:DataGridColumnHeader}" x:Key="DefaultColumnHeaderStyle">
<Setter Property="ContextMenu" Value="{DynamicResource columnHeaderMenu}" >
</Style>
This line goes in my constructor
public Window1()
{
this.DataContext = new AppData();
}
This code goes in my AppData class:
public class AppData
{
private IList<GridData> fullGridData = new ObservableCollection<GridData>();<br>
public IList<GridData> FullGridData
{
get { return fullGridData; }
set { fullGridData = value; }
}
private DelegateCommand<object> cutCommand;
public DelegateCommand<object> CutCommand
{
get
{
if (cutCommand == null)
{
cutCommand = new DelegateCommand<object>(CutColumn);
}
return cutCommand;
}
}
private void CutColumn(object obj)
{
//some code goes here
}
}
** I want to know exactly where am I doing wrong?? Why is the DataBinding not happening??
Please help me regarding this. Please provide me the sample code or modification in my present code from which I can achieve it. **
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您的代码(或当时使用的 WPF 版本(?))中的某些内容过于复杂。我可以进行绑定,例如
命令的设置位置如下:
Something in your code (or the version of WPF being used at the time(?)) is overcomplicating things. I am able to bind such as
Where the command is setup like this:
我有同样的问题。一旦我将命令绑定从代码隐藏移动到 ViewModel,命令绑定就停止工作。在视图模型中,我必须将 ICommand 从 RoutedCommand 更改为 DelegateCommand。我能够通过以下方式使其工作 -
将打开的事件处理程序添加到上下文菜单 -
在后面的代码中,您可以将 ViewModel 分配给上下文菜单的 DataContext -
I had the same issue. The command bindings stopped working once I moved them to the ViewModel from code behind. And in the viewmodel I had to change my ICommand from RoutedCommand to DelegateCommand. I was able to get it working in the following way -
Add Opened eventhandler to your context menu -
In the code behind, you would assign your ViewModel to the context menu's DataContext -
我通常在视图中将视图模型实例化为静态资源:
然后,即使当前绑定上下文不是视图模型,您也可以轻松引用视图模型的任何属性:
有关详细信息,请查看我的文章 实现 MVVM 和 XAML/.NET 应用程序的建议和最佳实践。
I usually instantiate my view model as static resource in my view:
Then you can easily reference any property of your view model even if the current binding context is not the view model:
For more information, have a look at my article Recommendations and best practices for implementing MVVM and XAML/.NET applications.
您有两个选择。
注意:我在此处添加的代码示例与您的示例类似,但不相同。
将 ContextMenu 的定义移动到 DataGrid 定义中,如下所示:
或者更好地将 CommandReference 添加到资源中,并将 MenuItem 中的 Command 设置为 StaticResource,如下所示:
You have two options.
Note: the code samples I added here a similar, but not same as your samples.
Move the definition of the ContextMenu inside the DataGrid defintion as follows:
Or better add a CommandReference to your Resources and set the Command in the MenuItem to a StaticResource as follows: