Why in VS2010 does a WPF application repeat all warnings twice and how do I stop that?

Question

In VS2010 create a new WPF application. In MainWindow.cs declare an unused local variable to generate a compiler warning like so:

namespace WpfApplication4
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            int i = 0;
        }
    }
}

Build the application. The output will appear something like this:

------ Rebuild All started: Project: WpfApplication4, Configuration: Debug x86 ------
D:\_UserData\Development\Workspaces\DotnetTesting\WpfApplication4\WpfApplication4\MainWindow.xaml.cs(25,8): warning CS0219: The variable 'i' is assigned but its value is never used

Compile complete -- 0 errors, 1 warnings
  WpfApplication4 -> D:\_UserData\Development\Workspaces\DotnetTesting\WpfApplication4\WpfApplication4\bin\Debug\WpfApplication4.exe
========== Rebuild All: 1 succeeded, 0 failed, 0 skipped ==========

Notice that there is only one mention of unused variable 'i'. Now in MainWindow.xaml add a reference to the local namespace like this:

<Window x:Class="WpfApplication4.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:WpfApplication4"
    Title="MainWindow" Height="350" Width="525">
    <Grid>

    </Grid>
</Window>

Now rebuild and the output appears like this:

------ Rebuild All started: Project: WpfApplication4, Configuration: Debug x86 ------
D:\_UserData\Development\Workspaces\DotnetTesting\WpfApplication4\WpfApplication4\MainWindow.xaml.cs(25,14): warning CS0219: The variable 'i' is assigned but its value is never used

Compile complete -- 0 errors, 1 warnings
MainWindow.xaml.cs(25,14): warning CS0219: The variable 'i' is assigned but its value is never used
  WpfApplication4 -> D:\_UserData\Development\Workspaces\DotnetTesting\WpfApplication4\WpfApplication4\bin\Debug\WpfApplication4.exe
========== Rebuild All: 1 succeeded, 0 failed, 0 skipped ==========

Notice that now there are two mentions of unused variable 'i'.

Why is that and how do I stop it from happening?

EDIT

I've worked out how to make it stop. Just add the name of the local assembly as well as the namespace like so:

<Window x:Class="WpfApplication4.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="clr-namespace:WpfApplication4;assembly=WpfApplication4"
    Title="MainWindow" Height="350" Width="525">
    <Grid>

    </Grid>
</Window>

Unfortunately that isn't a solution since in a WPF exe when refering to a namespace in the local assembly you you are not allowed to supply the name of the assembly in the namespace declaration. This will build, but if you try to reference a type in the local assembly it will fail if the assembly name is specified. Using the xmlns:local="clr-namespace:WpfApplication4;assembly=" syntax the double warnings return.

PS Why the down voting? Down voting without comment is lame, how am I supposed to improve the question if you don't tell me what you don't like about it?

Answer 1

It's because it's a bug in VS2010 that MS won't fix.

https://connect.microsoft.com/VisualStudio/feedback/details/763045/adding-a-xaml-namespace-reference-to-containing-assembly-corrupts-build-output