Set property 'Prism.Regions.RegionManager.RegionName' threw an exception - wpf

Question

I am working on an application for my office using WPF with Prism, and I've hit a roadblock. I found a webinar hosted by Brian Lagunas (one of the developers of Prism) that was doing several of the things that I need to do in this app, so I basically followed along and changed namespaces, etc to fit my app.
The Solution will compile but it throws an exception when I try to navigate using the ContentControl with Prism:RegionManager.RegionName.
The Solution has 2 projects. The first project calls the MainWindow of the 2nd project. My code is below.
Project 1 - MainWindow
namespace AdjusterToolV2
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow
{
public MainWindow()
{
InitializeComponent();
}
private void btnLetters_Click(object sender, RoutedEventArgs e)
{
URLetters.MainWindow frm1 = new URLetters.MainWindow();
frm1.Show();
}
}
}
Prism Bootstrapper
using Prism.Unity;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using Microsoft.Practices.Unity;
using URLetters.Views;
namespace URLetters
{
public class Bootstrapper : UnityBootstrapper
{
protected override DependencyObject CreateShell()
{
return Container.Resolve<MainWindow>();
}
protected override void InitializeShell()
{
Application.Current.MainWindow.Show();
}
protected override void ConfigureContainer()
{
base.ConfigureContainer();
Container.RegisterType(typeof(object), typeof(PHLtrWithEvidenceView), "PHLtrWithEvidenceView");
}
}
}
XAML for project 2 main page (code behind is empty)
<Controls:MetroWindow x:Class="URLetters.MainWindow"
xmlns= "http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:Controls="clr-namespace:MahApps.Metro.Controls;assembly=MahApps.Metro"
xmlns:d= "http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:prism="http://prismlibrary.com/"
prism:ViewModelLocator.AutoWireViewModel="True"
xmlns:local="clr-namespace:URLetters"
mc:Ignorable="d"
Title="Unresolved Liability Letters"
Height="500"
Width="700"
Icon="../Resources/GEICO.ico"
ResizeMode="NoResize"
WindowStartupLocation="CenterScreen">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="120"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<DockPanel Grid.Column="0" Background="#154995" HorizontalAlignment="Left" LastChildFill="False" Width="120">
<StackPanel Grid.Column="0">
<Button x:Name="btn48hrWithEvidence"
Command="{Binding NavigateCommand}"
CommandParameter="PHLtrWithEvidenceView"
x:FieldModifier="public"
Height="40"
Width="100"
Margin="10,10,0,0"
ToolTip="Letter to the PH with a 48 hour contact time limit. Used when evidence has been provided by the claimant" >
<TextBlock FontSize="11" Text="48 Hour - PH With Evidence" TextWrapping="Wrap" TextAlignment="Center" />
</Button>
<Button x:Name="btn48hrNoEvidence"
Height="40"
Width="100"
Margin="10,10,0,0"
ToolTip="Letter to the PH with a 48 hour contact time limit. Used when there is no evidence provided by the claimant" >
<TextBlock FontSize="11" Text="48 Hour - PH With No Evidence" TextWrapping="Wrap" TextAlignment="Center" />
</Button>
<Button x:Name="btnNoCtcPH"
Height="40"
Width="100"
Margin="10,10,0,0"
ToolTip="Letter to the PH advising them that we have reached an AT FAULT liability decision based on the evidence provided." >
<TextBlock FontSize="11" Text="No Contact - PH Liability Decision" TextWrapping="Wrap" TextAlignment="Center" />
</Button>
<Button x:Name="btnNoCtcPHLiabDenial"
Height="40"
Width="100"
Margin="10,10,0,0"
ToolTip="Letter to the PH advising them that we have denied liability because we have no evidence to support the PH involvement" >
<TextBlock FontSize="11" Text="No Contact - PH Liability Denial" TextWrapping="Wrap" TextAlignment="Center" />
</Button>
<Button x:Name="btnNoCtcCLMTLiabDenial"
Height="40"
Width="100"
Margin="10,10,0,0"
ToolTip="Letter to the CLAIMANT advising that we have denied liability because we have no evidence to support the PH involvement" >
<TextBlock FontSize="11" Text="No Contact - CLMT Liability Denial" TextWrapping="Wrap" TextAlignment="Center" />
</Button>
</StackPanel>
</DockPanel>
<DockPanel x:Name="ContentRegionName" Grid.Column="1">
<ContentControl prism:RegionManager.RegionName="ContentRegion"/>
</DockPanel>
</Grid>
</Controls:MetroWindow>
ViewModel for project 2 mainwindow
using Prism.Mvvm;
using Prism.Regions;
using Prism.Commands;
namespace URLetters.ViewModels
{
public class MainWindowViewModel : BindableBase
{
private readonly IRegionManager _regionManager;
public DelegateCommand<string> NavigateCommand { get; set; }
public MainWindowViewModel(IRegionManager regionManager)
{
_regionManager = regionManager;
NavigateCommand = new DelegateCommand<string>(Navigate);
}
private void Navigate(string uri)
{
_regionManager.RequestNavigate("ContentRegion", uri);
}
}
}
It throws the exception in the XAML file on this line:
<ContentControl prism:RegionManager.RegionName="ContentRegion"/>
exception reads: "Exception thrown: 'System.Windows.Markup.XamlParseException' in PresentationFramework.dll
Additional information: 'Set property 'Prism.Regions.RegionManager.RegionName' threw an exception.' Line number '69' and line position '14'."
This happens when I click the btnLetters button. The URLetters MainWindow does not open and then the exception is thrown. I've gone back over the code, and checked it against the examples in the webinar and I can't figure out why the exception is being thrown.. Help would be greatly appreciated.

Answer 1

It doesn't look like you have your application setup properly. Your Bootstrapper should be the class responsible for showing your MainWindow. You should not have any StartupUri in your App.xaml. There is obviously something wrong with how you have your project setup, but there is not enough information in your post for me to give a definite answer. Plus, having 2 MainWindows is confusing me :)
Download and install the Prism Template Pack: https://visualstudiogallery.msdn.microsoft.com/e7b6bde2-ba59-43dd-9d14-58409940ffa0
Then create a new Prism Unity App for WPF. It will stub out your application for you properly. Then just start adding your Views and ViewModels