Q:

How to Bind a WPF control to a WCF method using an ObjectDataProvider

I'm testing out WPF for the first time and I'm trying to call a WCF service with an ObjectDataProvider. 
WCF Service named WcfService1 with a single method:
namespace WcfService1
{
    public class Service1 : IService1
    {

        public String HelloWorld()
        {
            return "Hello World!";
        }
    }
}

I added a Service Reference to my WPF project and named it TestService
In my main window, I can call this without issue in code behind. It seems simple; like a web service call:
TestService.Service1Client service = new TestService.Service1Client();
MessageBox.Show(service.HelloWorld());
I'm trying to create an ObjectDataProvider that points to this service. I guess I'm confused as to what the ObjectType should be? I've tried local, the service namespace, src; I'm lost:
<Window.Resource>
    <ObjectDataProvider 
        x:Key="odpTestService" 
        ObjectType="{x:Type **TestService**:Service1Client}" 
        MethodName="HelloWorld" />
</Window.Resources>

Ultimatly it will bind to a TextBlock:
<TextBlock Grid.Column="0" Grid.Row="0" 
Grid.ColumnSpan="2" Background="AliceBlue"
Text="{Binding Source={StaticResource odpTestService}}" />

I was trying to work from the Flickr example posted here: http://khason.net/blog/wpf-binding-to-wcf-and-more/
Update:
The answer from Denis did solve part of the issue here. Now, I'm getting an error on compile:
System.Windows.Data Error: 34 : ObjectDataProvider: Failure trying to invoke method on type;
The ObjectDataProvider can't invoke the HelloWorld method with type IService1 (Using the method and type from my example). Any ideas why?

A:

You need to import the service's namespace through an xmlns directive at the top of the file:
Assuming that the reference has been added directly to your application, and that your application's root namespace is "MyApplication":
<Window x:class="MyApplication.MyWindow"
        xmlns:srv="MyApplication.TestService">

        <Window.Resource>
            <ObjectDataProvider 
                x:Key="odpTestService" 
                ObjectType="{x:Type srv:Service1Client}" 
                MethodName="HelloWorld" />
        </Window.Resources>

        <TextBlock Grid.Column="0" Grid.Row="0" 
          Grid.ColumnSpan="2" Background="AliceBlue"
          Text="{Binding Source={StaticResource odpTestService}}" />

</Window>

