How do I bind a datagrid column isreadonly property to a different property of the bound item

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This is probably easier to show in code than to ask in English.

I have a list in my view-model, something like this:

public class CostItems
{
	public string Name { get; set; } "";
	
	public double UnitCost { get; set; } = 0.0;
	
	public bool UnitCostFixed { get; set; } = false;
}


public List<CostItem> CostItems = new List<CostItem>();

And my XAML to display this is something like this:

<DataGrid Grid.Row="1" Grid.Column="0" ItemsSource="{Binding CostItems}"
	AutoGenerateColumns="False"
	HeadersVisibility="Column"
	SelectionUnit="Cell" SelectionMode="Single">
	<DataGrid.Columns>
		<DataGridTextColumn Header="Name" Binding="{Binding Name}"/>
		<DataGridTextColumn Header="Unit Cost">
			<DataGridTextColumn.Binding>
				<Binding Path="UnitCost" UpdateSourceTrigger="LostFocus">
					<Binding.ValidationRules>
						<u:CurrencyNonNegativeValidator/>
					</Binding.ValidationRules>
					<Binding.Converter>
						<u:CurrencyConverter/>
					</Binding.Converter>
				</Binding>
			</DataGridTextColumn.Binding>
		</DataGridTextColumn>
	</DataGrid.Columns>
</DataGrid>

What I am wanting to do is bind the IsReadOnly property of the DataGridTextColumn that displays the UnitCost to the UnitCostFixed property of the same item in the list.

I'm guessing I need some form of RelativeSource binding but can't work it out.

How do I do this?

What I have tried:

I've tried looking at the visual tree but it seems not to show enough detail (i.e. it stops at the DataGrid.

I have also tried increasing the debug info coming from the binding engine by setting :

diag:PresentationTraceSources.TraceLevel="High"

but don't seem to be getting much that is helping me.

Posted 29-Mar-20 22:58pm

Patrick Skelton

Updated 31-Mar-20 1:20am

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[no name] 31-Mar-20 4:17am

It's not logical: you want to tie a column property to a value in a "row" (i.e. item). This relates to the "cell".

Patrick Skelton 31-Mar-20 7:14am

Thanks for the reply. You are, of course, right. I realised soon after posting that what I was attempting just didn't make sense. I held back on a reply until I had got something that works, which I have now posted.

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Patrick Skelton · Answer 1 · 2020-03-31T01:21:00

This seems to do the trick. What I do is use a template column instead of a plain text column. Now I can swap templates for each individual cell based on properties to which that row in the grid are bound. So I then simply have one editable version of the template and one that is read-only.

<DataGrid ItemsSource="{Binding CostItems}"
	HeadersVisibility="Column"
	SelectionUnit="Cell"
	SelectionMode="Single">

	<DataGrid.Resources>
		<DataTemplate x:Key="UnitCostAllowModifyTemplate">
			<TextBox IsReadOnly="False" IsTabStop="True">
				<Binding Path="UnitCost" UpdateSourceTrigger="LostFocus"/>
			</TextBox>
		</DataTemplate>
		<DataTemplate x:Key="UnitCostBlockModifyTemplate">
			<TextBox IsReadOnly="True" IsTabStop="False">
				<Binding Path="UnitCost"/>
			</TextBox>
		</DataTemplate>
	</DataGrid.Resources>

	<DataGrid.Columns>
		<DataGridTextColumn Header="Name" Binding={Binding Name}"/>
		<DataGridTemplateColumn Header="Unit Cost">
			<DataGridTemplateColumn.CellTemplate>
				<DataTemplate>
					<ContentControl Content="{Binding .}">
						<ContentControl.Style>
							<Style TargetType="{x:Type ContentControl}">
								<Setter Property="KeyboardNavigation.IsTabStop" Value="False"/>
								<Setter Property="ContentTemplate" Value="{StaticResource UnitCostAllowModifyTemplate}" />
								<Style.Triggers>
									<DataTrigger Binding="{Binding UnitCostFixed}" Value="False">
										<Setter Property="ContentTemplate" Value="{StaticResource UnitCostBlockModifyTemplate}" />
									</DataTrigger>
								</Style.Triggers>
							</Style>
						</ContentControl.Style>
					</ContentControl>
				</DataTemplate>
			</DataGridTemplateColumn.CellTemplate>
		</DataGridTemplateColumn>
	</DataGrid.Columns>
</DataGrid>

Top Tip I found on the internet is to use a dummy converter on any binding you can't debug. Then you can break in the debugger and see exactly what object the binding is getting.