How do you restrict selection of cells to exclude a column in a DataGrid?

Question

I have a datagrid based selection control that duplicates the Easing Function selector in Expression Blend. This is for the Easing Function project so you will also be helping yourself :)

This selector is a permanent fixture on the screen, to make it easy to try out options, while still looking enough like the options you normally select from a drop-down in Blend:

I need to stop the current cell moving into the last "Heading" column.

Is there an easy way to restrict movement into columns so that only the first 3 columns are selectable?

Answer 1

I'd be inclined to do something like this:-

 <Grid>
    <Grid.ColumnDefinitions>
       <ColumnDefinition Width="150" />
       <ColumnDefinition Width="50" />
    </Grid.ColumnDefinitions>
    <Grid.RowDefinitions>
       <RowDefinition />
       <RowDefinition Height="250" />
    </Grid.RowDefinitions>
    <StackPanel Orientation="Horizontal" Grid.ColumnSpan="2">
       <!-- Heading Text Blocks -->
    </StackPanel>
    <ListBox ItemsSource="{Binding SetOfFunctions}" Grid.Row="1">
       <ListBox.ItemsPanel>
           <ItemsPanelTemplate>
               <toolkit:WrapPanel />
           </ItemsPanelTemplate>
       </ListBox.ItemsPanel>
    </ListBox>
    <ItemsControl ItemsSource="{Binding SetOfFunctionNames}" Grid.Row="1" Grid.Column="1" />
  </Grid>

Thats a basic skeleton idea, the only selector here is the ListView, appropriate sizing and ordering of source collections will arrive at the desired appearance.

Answer 2

Conceptually, the WPF and SL DataGrid stinks. Anything that requires dynamic relationships among rows and columns is hackish. For example, a cell's value cannot be computed at run-time w/o reflection on UI bindings, and is determined by the DataGrid's hardwired strategy for displaying a value in a cell. It assumes that Columns display a specific object in a Data Source, and it assumes that it knows how to walk that data source. (For what it is worth, I've argued this "successfully" (their words, not mine) to at least one WPF UI component vendor, and they might create a DataGrid that works this way.) If you're familiar with Ext.js, that's how DataGrid's work in that HTML/CSS/JS framework: DataGrid's have no knowledge of what to do with a DataSource, you have to tell it what to do. Everything is completely modularized and there is very little hardwiring of dependencies that can't be overwritten without reflection.

You are better off creating your own DataGrid-like control, especially if you don't have a large number of rows or columns to materialize. Your control should let you walk the DataSource however you want and supply information on how to render the cell and edit the cell. The cell editor should probably implement a Flyweight pattern to conserve memory, but only because that is a standard trick.