[Solved] GridViewComboBoxColumn Doesn't Always Display Selected Values

[Dan Pingel]

Hi,

I'm having an issue with the GridViewComboBoxColumn where the selected values for ALL of my rows don't always display.

The images I've attached show what I mean.  I have no clue how they'll post, but they're attached.

I am writing this using the MVVM pattern, so everything is binding to my View Model.  Also, I'm using RIA Services and the ADO.NET Entity Framework to pull data from my SQL Server Database.

In said database, I have two relevant tables:

Material
ID (int)
GaugeID (int)
Name (nvarchar(63))
Grade (nvarchar(63))
Thickness(numeric(5,4))
WeightPerSquareFoot(numeric(9,4))

Gauge
ID (int)
Name (nvarchar(63))

And, of course, there is a foreign key between Material.GaugeID and Gauge.ID.

So, here's the XAML for my RadGridView:

<telerik:RadGridView Grid.Row="0"
         ItemsSource="{Binding Materials}"
         SelectedItem="{Binding SelectedMaterial, Mode=TwoWay}"
         CanUserResizeColumns="False" CanUserInsertRows="False" CanUserFreezeColumns="False"
         AutoGenerateColumns="False" SelectionMode="Single" ShowGroupPanel="False">
    <telerik:RadGridView.RowStyle>
        <Style TargetType="telerik:GridViewRow">
            <Setter Property="MinHeight" Value="30"/>
        </Style>
    </telerik:RadGridView.RowStyle>
    <telerik:RadGridView.Columns>
        <telerik:GridViewToggleRowDetailsColumn />
        <telerik:GridViewDataColumn Header="Material Name" DataMemberBinding="{Binding Name}" Width="*" />
        <telerik:GridViewComboBoxColumn Header="Gauge"
                                        DataMemberBinding="{Binding GaugeID}"
                                        ItemsSource="{Binding Gauges}"
                                        DisplayMemberPath="Name"
                                        SelectedValueMemberPath="ID"
                                        Width="*"/>
        <telerik:GridViewDataColumn Header="Grade" DataMemberBinding="{Binding Grade}" Width="*" />
        <telerik:GridViewDataColumn Header="Thickness" DataMemberBinding="{Binding Thickness}"  Width="*" />
        <telerik:GridViewDataColumn Header="Wt. / Sq. Foot" DataMemberBinding="{Binding WeightPerSquareFoot}"  Width="*" />
    </telerik:RadGridView.Columns>
</telerik:RadGridView>

And the view model:

private IEnumerable<Material> materials;
public IEnumerable<Material> Materials {
    get { return materials; }
    private set {
        if (value != materials) {
            materials = value;
            RaisePropertyChanged("Materials");
        }
    }
}
private IEnumerable<Gauge> gauges;
public IEnumerable<Gauge> Gauges {
    get { return gauges; }
    private set {
        if (value != gauges) {
            gauges = value;
            RaisePropertyChanged("Gauges");
        }
    }
}
private Material selectedMaterial;
public Material SelectedMaterial {
    get { return this.selectedMaterial; }
    set {
        if (value != this.selectedMaterial) {
            this.selectedMaterial = value;
            this.RaisePropertyChanged("SelectedMaterial");
            DeleteMaterialCommand.RaiseCanExecuteChanged();
        }
    }
}

Materials and Gauges are both fetched from the RIA Services when the Page loads.

The values display correctly (when they display), and when I make changes to the values the changes stick.  I just can't get them to reliably display.  Any ideas?

Thanks,

-Dan Pingel

Materials and Gauges are both fetched from the RIA Services when the Page loads.The values display correctly (when they display), and when I make changes to the values the changes stick.  I just can't get them to reliably display.  Any ideas?Thanks,-Dan Pingel

[Glenn Dawson]

I have a similar visibility issue with the GridViewComboBoxColumn. The values are not visible but appear when I click on one of the cells in the column.

[Pavel Pavlov]

Hi guys,
Such behavior typically occurs when there is a problem in the ItemsSource binding of the combo column .

Having a view model as a DataContext of the grid and trying to bind to in generally would not work , as the DataContext of the cell would not be the view model , but the business object related to the row instead.

There are two ways of solving the issue :
1. Expose the view model as a static resource on the page so that it can be easily accessible by the binding .
or

2. Set the ItemsSource of the combo column in code behind instead of binding it in XAML .

If these do not help I would recommend to send me a runnable project so I can step trough it and see what  is causing the issue.

*To be able to attach the zip with the repro project, you may need to open a support ticket.

Best wishes,
Pavel Pavlov
the Telerik team

[Radoslaw]

One more important notice:

 

It is necessary to have the same data types binded to corresponding property: DataMemberBinding and SelectedValueMemberPath; even int32 and int64 cause GridViewComboBoxColumn do not display selected value.

[Pavel Pavlov]

Hi guys ,

Indeed form my experience the most common reason for such erroneous behavior is having the id in the combo source as integer and the matching id in the GridView source as string for example.

The second reason may be  trying to use element name binding.

Kind regards,
Pavel Pavlov
the Telerik team