Error 0x8007000b: Failed to create the managed bootstrapper application

I hope you are doing alright :)

So, I was doing some wix tutorials about Burn, Bootstrapper tool.

I tried to build my own UI (following this tutorial) and when I wanted to run it, it crashed.

I have included this to my AsseblyInfo.cs

[assembly: BootstrapperApplication(
    typeof(CustomBootstrapperApplication))]

This is my BootstrapperCore.config

<?xml version="1.0" encoding="utf-8" ?>
<!-- Copyright (c) .NET Foundation and contributors. All rights reserved. Licensed under the Microsoft Reciprocal License. See LICENSE.TXT file in the project root for full license information. -->


<configuration>
    <configSections>
        <sectionGroup name="wix.bootstrapper" type="Microsoft.Tools.WindowsInstallerXml.Bootstrapper.BootstrapperSectionGroup, BootstrapperCore">
            <section name="host" type="Microsoft.Tools.WindowsInstallerXml.Bootstrapper.HostSection, BootstrapperCore" />
        </sectionGroup>
    </configSections>
    <startup useLegacyV2RuntimeActivationPolicy="true">
        <supportedRuntime version="v4.0" />
        <supportedRuntime version="v2.0.50727" />
    </startup>
    <wix.bootstrapper>
        <!-- Example only. Use only if the startup/supportedRuntime above cannot discern supported frameworks. -->
        <!--
        <supportedFramework version="v4\Client" />
        <supportedFramework version="v3.5" />
        <supportedFramework version="v3.0" />
        -->

        <!-- Example only. Replace the host/@assemblyName attribute with assembly that implements BootstrapperApplication. -->
        <host assemblyName="CustomBA" />
    </wix.bootstrapper>
</configuration>

My libraryclass is called CustomBA.

Everything compiles fine, however when trying to run the *.exe output file, it doesnt work.

After taking a look into the logs I found this ...

[5364:3710][2020-07-22T13:53:50]i000: Loading managed bootstrapper application.
[5364:3710][2020-07-22T13:53:50]e000: Error 0x8007000b: Failed to create the managed bootstrapper application.
[5364:3710][2020-07-22T13:53:50]e000: Error 0x8007000b: Failed to create UX.
[5364:3710][2020-07-22T13:53:50]e000: Error 0x8007000b: Failed to load UX.
[5364:3710][2020-07-22T13:53:50]e000: Error 0x8007000b: Failed while running 

I have struggling for days. I can see that this problem arises from many years ago but no one comes with a solution for the new releases of netframework 4.8 and wix 3.11(which I think is the problem because the tutorial I am following uses NetF 3.5 and Wix 3.6 I think https://learning.oreilly.com/library/view/wix-36-a/9781782160427/ch16s07.html). Thats the reason i am comming up with a new post.

I hope someone could help me out with this. Kind regards :)

So, Like I said, I have seen too, I mean too many posts asking for help without a solution. However after whole days, I found out that the UI MVVM library class AND the bootstrapper application must be compiled with Release x86. I was compiling with x64 because my msi is built with such arch.

I hope It could be helpful for others.