MVVM issue with binding a combobox to a datagrid

Question

I have sort of a Master/Details view. I have some text boxes and a combo box bound to the selected item of the data grid. What I want is the text boxes and the combo box to populate with the data from the data grid when a row is selected. This part works fine. The issue I am having is when I change the value of the combo box the data grid field is not updating. I have implemented INotifyPropertyChanged, but it appears that I have something wrong. The data grid holds records of type user and the combo box in question has records of type role. The User entity has a navigation property to a RoleID. How can I ensure that the data grid will update when changing the role combo box in the details?

Thank you,

RG

Here is the XAML...

<UserControl x:Class="Compliance.Views.UserAdministrationView"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         xmlns:local="clr-namespace:Compliance"
         xmlns:views="clr-namespace:Compliance.Views"
         xmlns:helpers="clr-namespace:Compliance.Helpers"
         xmlns:vm="clr-namespace:Compliance.ViewModels"
         xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
         mc:Ignorable="d" 
         d:DesignHeight="1000" d:DesignWidth="800">
<UserControl.Resources>
    <helpers:ActiveStatusConverter x:Key="ActiveStatusConverter"/>
</UserControl.Resources>
<Grid>
    <Grid.RowDefinitions>
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
        <RowDefinition Height="Auto" />
    </Grid.RowDefinitions>
    <StackPanel Orientation="Vertical" HorizontalAlignment="Center" VerticalAlignment="Center" Grid.Row="0" Margin="15">
        <Label Content="User" Height="25" FontSize="14" HorizontalContentAlignment="Center" />
        <Grid HorizontalAlignment="Center" VerticalAlignment="Top" DataContext="{Binding ElementName=usersDG, Path=SelectedItem, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}">
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="Auto" />
                <ColumnDefinition Width="Auto" />
                <ColumnDefinition Width="Auto" />
                <ColumnDefinition Width="Auto" />
                <ColumnDefinition Width="Auto" />
                <ColumnDefinition Width="Auto" />
            </Grid.ColumnDefinitions>
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="Auto" />
                <RowDefinition Height="Auto" MinHeight="35" />
            </Grid.RowDefinitions>
            <telerik:Label Content="User Name: " Grid.Column="0" Grid.Row="0" HorizontalAlignment="Right" VerticalAlignment="Center" />
            <TextBox Grid.Column="1" Grid.Row="0" MinHeight="23" HorizontalAlignment="Left" VerticalAlignment="Center" MinWidth="180" MaxWidth="180" >
                <TextBox.Text>
                    <Binding Path="UserName" Mode="TwoWay" ValidatesOnDataErrors="True" NotifyOnValidationError="True" UpdateSourceTrigger="PropertyChanged"/>
                </TextBox.Text>                    
            </TextBox> 
            <telerik:Label Content="First Name: " Grid.Column="2" Grid.Row="0" HorizontalAlignment="Right" VerticalAlignment="Center" />
            <TextBox Grid.Column="3" Grid.Row="0" MinHeight="23" HorizontalAlignment="Left" VerticalAlignment="Center" MinWidth="180" MaxWidth="180">
            <TextBox.Text>
                <Binding Path="FirstName" Mode="TwoWay" ValidatesOnDataErrors="True" NotifyOnValidationError="True" UpdateSourceTrigger="PropertyChanged"/>
            </TextBox.Text>
            </TextBox>
            <telerik:Label Content="Last Name: " Grid.Column="4" Grid.Row="0" HorizontalAlignment="Right" VerticalAlignment="Center" />
            <TextBox Grid.Column="5" Grid.Row="0" MinHeight="23" HorizontalAlignment="Left" VerticalAlignment="Center" MinWidth="180" MaxWidth="180">
            <TextBox.Text>
                <Binding Path="LastName" Mode="TwoWay" ValidatesOnDataErrors="True" NotifyOnValidationError="True" UpdateSourceTrigger="PropertyChanged"/>
            </TextBox.Text>
            </TextBox>
            <telerik:Label Content="Email: " Grid.Column="0" Grid.Row="1" HorizontalAlignment="Right" VerticalAlignment="Center" />
            <TextBox Grid.Column="1" Grid.Row="1" MinHeight="23" HorizontalAlignment="Left" VerticalAlignment="Center" MinWidth="180" MaxWidth="180">
                <TextBox.Text>
                    <Binding Path="Email" Mode="TwoWay" ValidatesOnDataErrors="True" NotifyOnValidationError="True" UpdateSourceTrigger="PropertyChanged"/>
                </TextBox.Text>
            </TextBox>
            <telerik:Label Content="Active Status: " Grid.Column="2" Grid.Row="1" HorizontalAlignment="Right" VerticalAlignment="Center" />
            <telerik:RadComboBox x:Name="comBoxActiveStatus" Grid.Column="3" Grid.Row="1" MinHeight="23" MinWidth="180" HorizontalAlignment="Left" VerticalAlignment="Center"
                    SelectedItem="{Binding Path=ActiveStatus, 
                                    Converter={StaticResource ResourceKey=ActiveStatusConverter}, 
                                    Mode=TwoWay, 
                                    ValidatesOnExceptions=True, 
                                    NotifyOnValidationError=True,
                                    UpdateSourceTrigger=PropertyChanged}"
                    EmptyText="Please Set Active Status">
            </telerik:RadComboBox>
            <telerik:Label Content="Role: " Grid.Column="4" Grid.Row="1" HorizontalAlignment="Right" VerticalAlignment="Center" />
            <telerik:RadComboBox x:Name="cmbRoles" 
                        Grid.Column="5" 
                        Grid.ColumnSpan="3"
                        Grid.Row="1" 
                        MinHeight="23" 
                        HorizontalAlignment="Left" 
                        Margin="5" 
                        VerticalAlignment="Center" 
                        MinWidth="180" 
                        ItemsSource="{Binding}" 
                        DisplayMemberPath="RoleName" 
                        SelectedValue="{Binding RoleID, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                        SelectedValuePath="RoleID"
                        EmptyText="Please Choose A Role">
            <telerik:RadComboBox.ItemsPanel>
                <ItemsPanelTemplate>
                    <VirtualizingStackPanel />
                </ItemsPanelTemplate>
            </telerik:RadComboBox.ItemsPanel>
            </telerik:RadComboBox>
            <Button Grid.Column="0" Grid.Row="2" Grid.ColumnSpan="3" Content="Save User" Width="100"  />
            <Button Grid.Column="4" Grid.Row="2" Grid.ColumnSpan="3" Content="Add User"  Width="100"  />
        </Grid>
    </StackPanel>
    <Border CornerRadius="10" BorderThickness="5" Grid.Row="1" VerticalAlignment="Top" HorizontalAlignment="Center">
        <Grid HorizontalAlignment="Center" VerticalAlignment="Center">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="Auto" />
            </Grid.RowDefinitions>
            <Label Content="Users" Grid.Row="0" Height="25" FontSize="14" HorizontalContentAlignment="Center" />
            <telerik:RadGridView x:Name="usersDG" ItemsSource="{Binding Users}" AutoGenerateColumns="False" ShowGroupPanel="False" IsReadOnly="True">
                <telerik:RadGridView.Columns>
                    <telerik:GridViewDataColumn DataMemberBinding="{Binding UserName}" Header="User Name" />
                    <telerik:GridViewDataColumn DataMemberBinding="{Binding FirstName}" Header="First Name" />
                    <telerik:GridViewDataColumn DataMemberBinding="{Binding LastName}" Header="Last Name" />
                    <telerik:GridViewDataColumn DataMemberBinding="{Binding Email}" Header="Email" />
                    <telerik:GridViewDataColumn DataMemberBinding="{Binding Role.RoleName, Mode=TwoWay}" Header="Role Name" />
                    <telerik:GridViewDataColumn DataMemberBinding="{Binding ActiveStatus, Converter={StaticResource ActiveStatusConverter}}" Header="Active Status" />
                </telerik:RadGridView.Columns>
            </telerik:RadGridView>
        </Grid>
    </Border>
</Grid>

Answer 1

Your ComboBox bindings looks strange

You have ItemsSource="{Binding }" which suggests that the DataContext for the ComboBox is a collection of Role objects, however you also have SelectedValue="{Binding RoleID}, which suggests the DataContext contains a property called RoleId

In addition, your GridView binds to Role.RoleName, so I would expect you'd want to bind your ComboBox.SelectedValue to Role.RoleId or perhaps ComboBox.SelectedItem to the property Role if they reference the same Role object in memory.

So I would expect your ComboBox bindings to look something like

<ComboBox ItemsSource="{Binding Source={x:Static local:StaticLists.RoleList}}"
          SelectedValue="{Binding Role.RoleID}" ... />

or something like this:

<ComboBox ItemsSource="{Binding 
              RelativeSource={RelativeSource AncestorType={x:Type views:UserAdministrationView}},
              Path=DataContext.AvailableRoles}"
          SelectedItem="{Binding Role}" ... />

I'd suggest looking into what your ComboBox.DataContext is (I use Snoop for debugging things like this), and double-check that your bindings are correct