如何从ContextMenu绑定到MVVM中的WPF DataGridColumn？ [英] How to bind to WPF DataGridColumn in MVVM from ContextMenu?

问题描述

我有一个DataGrid与不同的列（TextBox，Combobox，DataPicker等）通过MVVM显示数据。现在我想在每个ColumnHeader上按所选列分组的ContextMenu，但是我无法访问列的绑定源（绑定路径）来告诉ViewModell要组合的列。当我第一次打开上下文菜单它工作正常，但是当我再次打开上下文菜单时，它仍然会从第一次传递SortMemberPath。我做错了什么？

XAML：

 < DataGrid资源> 
< ContextMenu x：Key =DataGridColumnHeaderMenu> 
< MenuItem Name =mi_groupHeader =分组
 Command ={Binding RelativeSource = {RelativeSource FindAncestor，AncestorType = {x：Type local：MainWindow}}，Path = DataContext.GroupColumn} 
 CommandParameter ={Binding Path = Column.SortMemberPath，RelativeSource = {RelativeSource Mode = FindAncestor，AncestorType = DataGridColumnHeader}}> 
< / MenuItem>< / ContextMenu> 
< Style TargetType ={x：Type DataGridColumnHeader}> 
< Setter Property =ContextMenuValue ={StaticResource DataGridColumnHeaderMenu}/> 
< / Style> 
< /DataGrid.Resources> 
  

ViewModel：

 code> public ICommand GroupColumn 
 {
 get 
 {
 if（groupColumn == null）
 {
 groupColumn = new RelayCommand（（param ）=> {
 
 UngroupColumns.Execute（null）; 
 string groupPropertyName = param as string; ///不要此Switch。ViewModel不知道标题名称
 
 switch（groupPropertyName）
 {
 caseProject：{groupPropertyName =project_id; break;} 
 caseDate：{groupPropertyName =date ; break;} 
 casePerson：{groupPropertyName =person_id; break;} 
 default：{groupPropertyName = null; break;} 
} 
 
 if（groupPropertyName！= null）
 {
 MyData.GroupDescriptions.Add（new PropertyGroupDescription（groupPropertyName））; 
 MyData.SortDescriptions.Add（new SortDescription（groupPropertyName，ListSortDirection.Ascending））; 
} 
}）; 
} 
 
 return groupColumn; 
} 
} 
  

解决方案

我终于找到了解决问题的方法 here 。
但是我仍然不明白为什么CommandParameters在我尝试使用时不会更新：

  CommandParameter ={ Binding RelativeSource = {RelativeSource Mode = FindAncestor，AncestorType = {x：Type DataGridColumnHeader}}，Path = Column.SortMemberPath}
  

所以这里是适用于我的代码：

 < DataGrid.Resources> 
< ContextMenu x：Key =DataGridColumnHeaderMenu> 
< MenuItem Name =mi_groupHeader =Make Groups
 Command ={Binding RelativeSource = {RelativeSource FindAncestor，AncestorType = {x：Type local：MainWindow}}，Path = DataContext.GroupColumn }
 CommandParameter ={Binding RelativeSource = {RelativeSource Mode = FindAncestor，AncestorType = {x：Type ContextMenu}}，Path = PlacementTarget.Column.SortMemberPath}> 
< MenuItem.Icon> 
< Image Source =images / Treeview.png/> 
< /MenuItem.Icon> 
< / MenuItem> 
< / ContextMenu> 
< Style TargetType ={x：Type DataGridColumnHeader}> 
< Setter Property =ContextMenuValue ={StaticResource DataGridColumnHeaderMenu}/> 
< / Style>< /DataGrid.Resources> 
  

在我的情况下使用SortMemberPath的优点是我还可以检索DataGridComboxColumn的值（SelectedValuePath） 。假设SelectedValuePath等于SortMemberPath，这在我的情况下。

ViewModel：

  private RelayCommand groupColumn; 
 public ICommand GroupColumn 
 {
 get 
 {
 if（groupColumn == null）
 groupColumn = new RelayCommand（
（param）= > 
 {
 UngroupColumns.Execute（null）; 
 
 // param包含DataGridColumn的SortMemberPath 
 string groupPropertyName = param as string; 
 
 if（groupPropertyName！= null）
 {
 MyData.GroupDescriptions.Add（new PropertyGroupDescription（groupPropertyName））; 
 MyData.SortDescriptions.Add（new SortDescription（groupPropertyName，ListSortDirection.Ascending ））; 
} 
 
}）; 
 
 return groupColumn; 
} 
} 
  

I have a DataGrid with different Columns (TextBox, Combobox, DataPicker, etc.) displaying Data via MVVM. Now I want to have ContextMenu on each ColumnHeader to Group by the selected column, but I can't access the Binding Source (Binding Path) of the Column to tell ViewModell which column it has to Group. When I open the context menu for the first time it works fine, but when I open the context menu once again, it still passes the SortMemberPath from the first time. What am I doing wrong?

XAML:

<DataGrid.Resources>
    <ContextMenu x:Key="DataGridColumnHeaderMenu">
        <MenuItem Name="mi_group" Header="Grouping"                                             
                  Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:MainWindow}}, Path=DataContext.GroupColumn}"
                  CommandParameter="{Binding Path=Column.SortMemberPath, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=DataGridColumnHeader}}">
        </MenuItem></ContextMenu>
    <Style TargetType="{x:Type DataGridColumnHeader}">
        <Setter Property="ContextMenu" Value="{StaticResource DataGridColumnHeaderMenu}" />
    </Style>
</DataGrid.Resources>

ViewModel:

public ICommand GroupColumn
{
    get
    {
        if (groupColumn == null)
        {
            groupColumn = new RelayCommand( (param) => {

                    UngroupColumns.Execute(null);
                    string groupPropertyName = param as string;   ///Don't want this Switch. ViewModel doesn't know name of the header

                    switch (groupPropertyName)
                    {
                        case "Project": {groupPropertyName = "project_id"; break;}
                        case "Date":    {groupPropertyName = "date";       break;}
                        case "Person":  {groupPropertyName = "person_id";  break;}
                        default:        {groupPropertyName = null; break;        }
                    }

                    if (groupPropertyName != null)
                    {
                        MyData.GroupDescriptions.Add(new PropertyGroupDescription(groupPropertyName));
                        MyData.SortDescriptions.Add(new SortDescription(groupPropertyName, ListSortDirection.Ascending));
                    }
                });
        }

        return groupColumn;
    }
}

解决方案

So I've finally found a solution to my problem here. But I still don't understand why CommandParameters is not updating when I try to use:

CommandParameter="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type DataGridColumnHeader}}, Path=Column.SortMemberPath}"

So here is the code that works for me:

<DataGrid.Resources>    
<ContextMenu x:Key="DataGridColumnHeaderMenu">
    <MenuItem Name="mi_group" Header="Make Groups"                                             
              Command="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:MainWindow}}, Path=DataContext.GroupColumn}"
              CommandParameter="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ContextMenu}}, Path=PlacementTarget.Column.SortMemberPath}">                        
        <MenuItem.Icon>
            <Image Source="images/Treeview.png" />
        </MenuItem.Icon>
    </MenuItem>     
</ContextMenu>
<Style TargetType="{x:Type DataGridColumnHeader}">
    <Setter Property="ContextMenu" Value="{StaticResource DataGridColumnHeaderMenu}" />
</Style></DataGrid.Resources>

The Advantage of using SortMemberPath in my case was that I could retrieve also a value (SelectedValuePath) for DataGridComboxColumn. Assumed that SelectedValuePath is equal to SortMemberPath which is in my case.

ViewModel:

    private RelayCommand groupColumn;
public ICommand GroupColumn
{
    get
    {
        if (groupColumn == null)
            groupColumn = new RelayCommand(
                (param) =>
                {
                    UngroupColumns.Execute(null);

                    // param contains SortMemberPath of the DataGridColumn
                    string groupPropertyName = param as string;

                    if (groupPropertyName != null)
                    {
                        MyData.GroupDescriptions.Add(new PropertyGroupDescription(groupPropertyName));
                        MyData.SortDescriptions.Add(new SortDescription(groupPropertyName, ListSortDirection.Ascending));
                    }

                });

        return groupColumn;
    }
}

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