Cannot read input from Bootstrapper variable in Ma

I have programmed setup with a managed bootstrapper application. In my solution are the following projects: - Setup.msi : The MSI-project to install - Setup.UI.dll : The WPF-GUI for the installation process - Bootstrapper.exe : The bootstrapper-project - Launcher.exe : A WPF-app to start the bootstrapper

In the bootstrapper bundle i have defined a variable for the installationfolder:

<Variable Name="INSTALLFOLDER"
          bal:Overridable="yes"
          Type="string"
          Value="[ProgramFilesFolder]"/>

This variable can be set by the Launcher when starting the bootstrapper:

    Process proc = new Process();
    proc.StartInfo.FileName = "msiexec";
    proc.StartInfo.FileName = "..\\..\\..\\Bootstrapper\\bin\\Debug\\Bootstrapper.exe";
    proc.StartInfo.Arguments = "IsClientSetup=true INSTALLFOLDER=C:\\TestSetup";
    proc.Start();

In case i'm using the standard bootstrapper (WixStandardBootstrapperApplication.RtfLicense) my given entry will be used in the defined variable INSTALLFOLDER. I see only the bootstrapper dialog while the installation process, but after all everythings fine.

But when i use the managed bootstrapper, which starts my WPF-GUI, and i try to read the installationpath, i always get the default from the definition: the programfilesfolder.

Here the code from the bundle:

<WixVariable Id="WixMbaPrereqPackageId"
             Value="Netfx4Full" />
<WixVariable Id="WixMbaPrereqLicenseUrl"
             Value="NetfxLicense.rtf" />
<BootstrapperApplicationRef Id="ManagedBootstrapperApplicationHost" >
    <Payload Name='BootstrapperCore.config' SourceFile='..\..\..\Setup.UI\bin\Debug\BootstrapperCore.config' />
    <Payload SourceFile='..\..\..\Setup.UI\bin\Debug\SetupUI.dll' />
</BootstrapperApplicationRef>

<Chain>
    <MsiPackage Id="SetupPackage"
                SourceFile="..\..\..\Setup.Msi\bin\Debug\Setup.msi"
                Cache="yes"
                DisplayInternalUI="no"
                Vital="yes"
                Compressed="no"
                EnableFeatureSelection="no"
                DisplayName="SetupForTest">
        <MsiProperty Name="INSTALLLOCATION"
                     Value="[INSTALLFOLDER]" />
</Chain>

And the code from the ViewModel in SetupUI:

string installationPath = UI.Model.Bootstrapper.Engine.FormatString(UI.Model.Bootstrapper.Engine.StringVariables["INSTALLFOLDER"]);

And - at least - the Run-method in the SetupUI:

protected override void Run()
{
    MessageBox.Show("1 = " + this.Engine.FormatString(this.Engine.StringVariables["INSTALLFOLDER"]));
    Model = new Model(this);
    Model.Bootstrapper.Engine.Detect();
    MessageBox.Show("2 = " + Model.Bootstrapper.Engine.FormatString(Model.Bootstrapper.Engine.StringVariables["INSTALLFOLDER"]));

    RootViewViewModel viewModel = new RootViewViewModel();
    View = new RootView(viewModel);

    // Populate the view models with data then run the view..
    viewModel.Refresh();
    View.Run();

    this.Engine.Quit(0);
}

Can anybody tell me, what i have made wrong?

I've found it myself! The code is correct, but when using a mannaged bootstrapper, the variables are not overwritten. So we have to read them in the SetupUI from the CommandLineArguments of the BootstrapperApplication and set them in the variable. That's all.