Databinding Enum to ComboBox

Question

I'm getting a very unusual error on a project that use to work where I'm trying to bind an ENUM to a combo box. To ensure I've not made coding errors, I've made a new usercontrol using SO Question 58743 and ageektrapped as samples for a self contained user control. I'm using .Net4 Client Framework as the environment and VS2010. The xaml is -

<UserControl x:Class="Barcode.Views.UserControl1" 
             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:System="clr-namespace:System;assembly=mscorlib"  
             mc:Ignorable="d" d:DesignHeight="300" d:DesignWidth="300">

    <UserControl.Resources>
        <ObjectDataProvider MethodName="GetValues" 
                            ObjectType="{x:Type System:Enum}" 
                            x:Key="AlignmentValues">
            <ObjectDataProvider.MethodParameters>
                <x:Type TypeName="HorizontalAlignment" />
            </ObjectDataProvider.MethodParameters>
        </ObjectDataProvider>
    </UserControl.Resources>
    <Grid>
        <ComboBox Name="myComboBox" SelectedIndex="0" Margin="8" 
                  ItemsSource="{Binding Source={StaticResource AlignmentValues}}" />
    </Grid>
</UserControl>

The error that I'm getting on the ComboBox is Error 144 Unable to cast object of type 'System.String' to type 'System.Windows.DataTemplate' after building the project.

I'm at a loss as to what could be causing this error.

Aaron McIver · Accepted Answer · 2011-01-21T17:24:16.417

1

Looks like you may be missing the namespace on your HorizontalAlignment. Add a relevant namespace where the HorizontalAlignment type resides.

xmlns:local="clr-namespace:Barcode.Views"

Then modify your XAML to make use of the newly defined namespace...

...

<x:Type TypeName="local:HorizontalAlignment"/>

...

EDIT:

With this being the HorizontalAlignment enum type from within the framework then your code should work as is. I tested it to be certain and it indeed works; as I placed an instance of the UserControl on my Window and it worked without a hitch. Set up an empty project and start from scratch to see if the problem still exists as you may have other factors causing the issue.

edited Jan 21 '11 at 17:24

answered Jan 21 '11 at 17:06

Aaron McIver

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Actually for this demo, I was trying to get the Horizontal alignment enums (left, right, center) as a know enum that works. This is how many of the demos have been written. – photo_tom Jan 21 '11 at 17:17
@photo_tom Added addition commentary, just copied/pasted your code and it does indeed work – Aaron McIver Jan 21 '11 at 17:24
@Aaron - That what is I've seen. However, in this project and another new project, I cannot get the code to run without the error. – photo_tom Jan 21 '11 at 17:31
@photo_tom So you went to add new UserControl and selected WPF UserControl (not WinForms) within the IDE then copied/pasted the above code and changed the x:Class for the UserControl and it will not compile? – Aaron McIver Jan 21 '11 at 17:45
@Aaron - After compile, the combo box is reporting being in an error state. If I go to run it, I will be a XAML parsing error. But I just tried building a completely new solution and it works there. There must be something corrupt in my solution, but I cannot figure out what. – photo_tom Jan 21 '11 at 18:00
@photo_tom Could be global templates within your App.xaml or other embedded resource. Make sure you have all your varying templates commented out in some fashion and see what happens. – Aaron McIver Jan 21 '11 at 18:04
@Aaron - That was it. There is a problem with global template. Thanks. – photo_tom Jan 21 '11 at 18:09

Databinding Enum to ComboBox

1 Answers1