Question

I have the following sample from MSDN:

<Grid x:Name="LayoutRoot" Background="White">
    <Grid.RowDefinitions>
        <RowDefinition Height="25" />
        <RowDefinition Height="Auto" />
    </Grid.RowDefinitions>
    <riaControls:DomainDataSource Name="source" QueryName="GetProductsByColor" AutoLoad="true">
        <riaControls:DomainDataSource.DomainContext>
            <domain:ProductDomainContext />
        </riaControls:DomainDataSource.DomainContext>
        <riaControls:DomainDataSource.QueryParameters>
            <riaControls:Parameter ParameterName="color" Value="{Binding ElementName=colorCombo, Path=SelectedItem.Content}" />
        </riaControls:DomainDataSource.QueryParameters>
    </riaControls:DomainDataSource>
    <ComboBox Width="60"  Grid.Row="0" x:Name="colorCombo">
        <ComboBoxItem Content="Black" />
        <ComboBoxItem Content="Blue" />
    </ComboBox>
    <data:DataGrid Grid.Row="1" ItemsSource="{Binding Data, ElementName=source}" />
</Grid>

Well, as you can see the line that creates a parameter binding is set:

<riaControls:Parameter ParameterName="color" Value="{Binding ElementName=colorCombo, Path=SelectedItem.Content}" /> 

However if I am to try this with code it doesn’t work:

Binding binding = new Binding();
binding.ElementName = "colorCombo";
//binding.Source = this.colorCombo; also doesn't work!
binding.Path = new PropertyPath("SelectedItem.Content");
binding.Mode = BindingMode.OneWay;

Parameter param = new Parameter();
param.Value = binding;

source.QueryParameters.Clear();
source.QueryParameters.Add(param);

Any ideas on what I am doing wrong?

Answer 1

To bind programmatically, you have to use BindingOperations.SetBinding. Currently you’re just setting the Value property to a Binding instance rather than binding it.

BindingOperations.SetBinding(param, Parameter.ValueProperty, binding)

Plus, change back your binding to Source = this.colorCombo. Element names are usually resolved within a XAML context, which is no present in code behind.