我有一个WPF DataGrid，我希望使用MVVM添加ContextMenu。这个DataGrid位于UserControl（我删除了一堆我认为与问题的本质无关的内容）：
<UserControl x:Class="Legend.MarkerMultiStatisticsControl"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:legend="clr-namespace:Legend"
Name="Self"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="300">
<GroupBox Header="{Binding ElementName=Self, Path=StaisticsData.Title}">
<DockPanel>
<DataGrid
DataContext="{Binding ElementName=Self}"
ItemsSource="{Binding ElementName=Self, Path=StaisticsData.Statistics}"
SelectionMode="Single"
CurrentCell="{Binding ElementName=Self, Path=CurrentCell, Mode=OneWayToSource}">
<DataGrid.ContextMenu>
<ContextMenu DataContext="{Binding RelativeSource={RelativeSource Mode=Self}, Path=PlacementTarget.DataContext}"
ItemsSource="{Binding Path=Commands}">
<ContextMenu.ItemContainerStyle>
<Style TargetType="MenuItem">
<Setter Property="Header" Value="{Binding Header}"></Setter>
<Setter Property="Command" Value="{Binding Command, diag:PresentationTraceSources.TraceLevel=High}"></Setter>
<Setter Property="CommandParameter" Value="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType=DataGrid}, Path=DataContext.CurrentLegendCell}"></Setter>
</Style>
</ContextMenu.ItemContainerStyle>
</ContextMenu>
</DataGrid.ContextMenu>
</DataGrid>
</DockPanel>
</GroupBox>
</UserControl>
此控件有一个名为DependencyProperty的{{1}}我绑定菜单Command，其类型为ItemsSource，ObservableCollection<LegendCommand>为< / p>
LegendCommand这些命令在视图模型的不同位置生成。
在一个地方（public class LegendCommand : ObservableObject
{
private string _header;
private ICommand _command;
public string Header
{
get { return _header; }
set { Set(()=>Header, ref _header, value); }
}
public ICommand Command
{
get { return _command; }
set { Set(() => Command, ref _command, value); }
}
}
班级内Adapter与对照Commands绑定）我有以下内容：
Commands在另一个地方（持有Commands.Add(new LegendCommand
{
Header = "From inside adapter...",
Command = new RelayCommand<LegendCellInfo>(info =>
{
MessageBox.Show(string.Format("State: {0}, Property: {1}", info.State, info.PropertyName));
})
});
的视图模型）我有以下内容：
Adapter我的问题是＆＃34;来自内部适配器......＆＃34;命令被执行但是＆＃34;选择＆＃34; ISN＆＃39;吨。我在＆＃34; Select＆＃34;中添加了一个断点。代码，但它从未被调用。
adapter.Commands.Add(new LegendCommand
{
Header = "Select",
Command = new RelayCommand<LegendCellInfo>(info =>
{
// selection logic
})
});
＆＃39; ContextMenu与ItemsSource属性的绑定有效，因为我在菜单中看到了两个选项。
Commands的绑定可能有效，因为其中一个命令已执行。
我调试了代码和绑定，并提供以下信息：
ICommans集合包含两个元素，其哈希码为40262542和26818564（在Visual Studio的立即窗口中运行Commands和adapter.Commands[0].Command.GetHashCode()得到它们。）
当我右键单击adapter.Commands[1].Command.GetHashCode()：
DataGrid如果我理解正确，我们可以看到发生了两个绑定操作 - 第一个绑定到System.Windows.Data Warning: 56 : Created BindingExpression (hash=11440639) for Binding (hash=54536677)
System.Windows.Data Warning: 58 : Path: 'Command'
System.Windows.Data Warning: 60 : BindingExpression (hash=11440639): Default mode resolved to OneWay
System.Windows.Data Warning: 61 : BindingExpression (hash=11440639): Default update trigger resolved to PropertyChanged
System.Windows.Data Warning: 62 : BindingExpression (hash=11440639): Attach to System.Windows.Controls.MenuItem.Command (hash=54276594)
System.Windows.Data Warning: 67 : BindingExpression (hash=11440639): Resolving source
System.Windows.Data Warning: 70 : BindingExpression (hash=11440639): Found data context element: MenuItem (hash=54276594) (OK)
System.Windows.Data Warning: 78 : BindingExpression (hash=11440639): Activate with root item LegendCommand (hash=5940773)
System.Windows.Data Warning: 108 : BindingExpression (hash=11440639): At level 0 - for LegendCommand.Command found accessor RuntimePropertyInfo(Command)
System.Windows.Data Warning: 104 : BindingExpression (hash=11440639): Replace item at level 0 with LegendCommand (hash=5940773), using accessor RuntimePropertyInfo(Command)
System.Windows.Data Warning: 101 : BindingExpression (hash=11440639): GetValue at level 0 from LegendCommand (hash=5940773) using RuntimePropertyInfo(Command): RelayCommand`1 (hash=40262542)
System.Windows.Data Warning: 80 : BindingExpression (hash=11440639): TransferValue - got raw value RelayCommand`1 (hash=40262542)
System.Windows.Data Warning: 89 : BindingExpression (hash=11440639): TransferValue - using final value RelayCommand`1 (hash=40262542)
System.Windows.Data Warning: 56 : Created BindingExpression (hash=31617173) for Binding (hash=54536677)
System.Windows.Data Warning: 58 : Path: 'Command'
System.Windows.Data Warning: 60 : BindingExpression (hash=31617173): Default mode resolved to OneWay
System.Windows.Data Warning: 61 : BindingExpression (hash=31617173): Default update trigger resolved to PropertyChanged
System.Windows.Data Warning: 62 : BindingExpression (hash=31617173): Attach to System.Windows.Controls.MenuItem.Command (hash=16119107)
System.Windows.Data Warning: 67 : BindingExpression (hash=31617173): Resolving source
System.Windows.Data Warning: 70 : BindingExpression (hash=31617173): Found data context element: MenuItem (hash=16119107) (OK)
System.Windows.Data Warning: 78 : BindingExpression (hash=31617173): Activate with root item LegendCommand (hash=16131920)
System.Windows.Data Warning: 107 : BindingExpression (hash=31617173): At level 0 using cached accessor for LegendCommand.Command: RuntimePropertyInfo(Command)
System.Windows.Data Warning: 104 : BindingExpression (hash=31617173): Replace item at level 0 with LegendCommand (hash=16131920), using accessor RuntimePropertyInfo(Command)
System.Windows.Data Warning: 101 : BindingExpression (hash=31617173): GetValue at level 0 from LegendCommand (hash=16131920) using RuntimePropertyInfo(Command): RelayCommand`1 (hash=26818564)
System.Windows.Data Warning: 80 : BindingExpression (hash=31617173): TransferValue - got raw value RelayCommand`1 (hash=26818564)
System.Windows.Data Warning: 89 : BindingExpression (hash=31617173): TransferValue - using final value RelayCommand`1 (hash=26818564)
，第二个绑定到'RelayCommand'1 (hash=40262542) - 顺便说一句，这些是我的两个命令的哈希码。
此外，不会发生例外或其他错误。
我陷入了调查之中。还有什么地方可以看？
更新1 ： 当我更改＆＃34中的代码时;选择＆＃34;命令以下代替我之前的代码：
'RelayCommand'1 (hash=26818564)然后代码突然开始工作......
更新2 ：
原始命令使用adapter.Commands.Add(new LegendCommand
{
Header = "Select",
Command = new RelayCommand<LegendCellInfo>(info =>
{
MessageBox.Show("yes");
})
});
类的成员。在线搜索MVVMLight Adapter和成员函数的问题，发现了这个问题：RelayCommand with Argument throwing MethodAccessException
（但显然我想继续使用MVVMLight ......）
更新3 ：读取RelayCommand的MVVMLight代码并且它不会保存对方法的硬引用，所以我认为没有什么能保持lambda活着。现在将重构代码并在此处更新（如果有效）。
答案 0 :(得分：7)
实际上，原因是MVVMLight的弱引用并未使“选择”命令保持活跃状态。 我在这里更详细地写了这篇文章：http://blogs.microsoft.co.il/dinazil/2015/01/16/relaycommands-weakfuncs/