<esri:MapProgressBar x:Name="MyProgressBar" Background="{StaticResource CommonBackgroundBrush}" Map="{Binding ElementName=Map}" HorizontalAlignment="Center" VerticalAlignment="Bottom" Width="150" Height="12" Margin="5" />
xmlns:esri="http://schemas.esri.com/arcgis/client/2009" <esri:MapProgressBar x:Name="MyProgressBar" Map="{Binding ElementName=myMap}" Grid.Row="1" HorizontalAlignment="Center" VerticalAlignment="Center" Width="150" Height="12" Margin="5" />