Button inside DataGrid wpf MVVM

Question

I am following MVVM in this project.

I have WPF datagrid,

ItemsSource (ItemsSource="{Binding Documents}") binded to an ObservableCollection<Document>,

SelectedItem (SelectedItem="{Binding CurrentDocument, Mode=TwoWay}") binded to WorkQueueDocument,

I also have used Interaction Triggers to capture the Double click of the mouse - in order to load the selected Document in a New WIndow.

<i:Interaction.Triggers>
    <i:EventTrigger EventName="MouseDoubleClick">
        <i:InvokeCommandAction Command="{Binding ShowViewerCommand}" />
    </i:EventTrigger>
</i:Interaction.Triggers>

I Have defined/binded the columns of my datagrid to corresponding attibutes of WorkQueueDocument class.

<DataGrid.Columns>
    <DataGridTextColumn Width="Auto"
                            MinWidth="100"
                            Header="Name"                                                            
                            Binding="{Binding Name}">
        <DataGridTextColumn.ElementStyle>
            <Style TargetType="{x:Type TextBlock}">
                <Setter Property="Margin" Value="2,0,0,0" />
                <Setter Property="ToolTip" Value="{Binding Name}" />
            </Style>
        </DataGridTextColumn.ElementStyle>
    </DataGridTextColumn>

    <!-- Many Other Columns Here... -->
</DataGrid.Columns>

<DataGrid.ColumnHeaderStyle>
        <!-- I have various designer style's properties defined here -->
</DataGrid.ColumnHeaderStyle>

---

I am supposed to load the document when the user selects the row (document) in the grid - for that CurrentDocument property is defined as follows:

public WorkQueueDocument CurrentDocument
{
    get
    {
        return this.currentDocument;
    }
    set
    {

        if (this.currentDocument != value)
        {
            this.currentDocument = value;
            this.OnPropertyChanged("CurrentDocument");
            this.IsDocumentSelected = true;

    // If we are in progress already, don't do anything
            if (!IsLoading && this.currentDocument != null)
            {
                IsLoading = true;
                LoadDocumentBackgroundWorker();// loading documenting async
            }


            if (this.currentDocument == null)
            {
                this.IsDocumentSelected = false;
            }
        }

    }
}

Now, the problem is - I want to add a Delete Button column to this datagrid, such that when user presses Delete button - the document gets deleted directly without loading the document. I added following xaml to <DataGrid.Columns>

<DataGridTemplateColumn.CellTemplate>
    <DataTemplate>
    <Button Name="DeleteBatch" 
            Content="Delete"
            Command="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type DataGrid}}, Path=DataContext.DeleteCommand}"
            CommandParameter="Delete"/>
    </DataTemplate>
</DataGridTemplateColumn.CellTemplate>

This DeleteCommand ain't getting fired. I tried to figure out WHY and discovered that I have

1st command is in datagrid for loading document on selection of row

ItemsSource="{Binding Documents}"

2nd command is on delete button which is in coluumn of above datagrid

<Button Name="Delete" 
Content="Delete" 
Command="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type DataGrid}}, Path=DataContext.DeleteCommand}" 
CommandParameter="Delete">

, I am able to access only one command at a time. When i click the button - the row ('obviously') gets selected and executed associated binding for 'SelectedItem' but does not follow up calling the

DeleteCommand ( which ideally should ) . But if I remove this 'SelectedItem' property - the deleteCommand gets triggered ( but then i dont get the selected row).

Also (while debugging i noticed) the **DeleteCommand gets executed on when we press(click) second time (coz now the row is already selected)**

I googled - and found few probable solutions, like Priority Binding and Tunneling , but unable to implement. Please guide me through this.

I got this link , but not sure if this is the only way.

P.S : 1. I am using WPF , .Net 4.0 and MVVM

2. Please do not suggest Third Party solutions. [unless the only option]

Answer 1

• The delete command parameter should just be

  CommandParameter="{Binding}"

• this means that the command parameter is the document reference itself thus you can do the following in your command

  yourDocumentObservableCollection.Remove(CommandParameter)

This way you wont need to care about if the Document is focused or not.