WPF中DataGrid双击命令获取选中的ViewModel

<DataGrid  x:Name="myGrd"
ItemsSource="{Binding SearchItems}"
SelectedItem="{Binding SelectedItem}"
SelectionMode="Single"
SelectionUnit="FullRow">

<i:Interaction.Triggers>
<i:EventTrigger EventName="MouseDoubleClick">
<cmd:EventToCommand Command="{Binding MouseDoubleClickCommand}"
CommandParameter="{Binding ElementName=myGrd, Path=SelectedItem}" />
</i:EventTrigger>
</i:Interaction.Triggers>
...
</DataGrid>

public ICommand MouseDoubleClickCommand
{
get
{
if (mouseDoubleClickCommand == null)
{
mouseDoubleClickCommand = new RelayCommand<SearchItem>(
item =>
{
var selectedetitem = item;
}
);
}
return mouseDoubleClickCommand;
}
}