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I'm trying to build a project using the classes in Microsoft.Build.

The code is:

var project = new ProjectInstance(CS_PROJ_FILE);

However it's throwing the following exception:

Microsoft.Build.Shared.InternalErrorException occurred
  Message=MSB0001: Internal MSBuild Error: Type information for Microsoft.Build.Utilities.ToolLocationHelper was present in the whitelist cache as Microsoft.Build.Utilities.ToolLocationHelper, Microsoft.Build.Utilities.Core, Version=, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a but the type could not be loaded. unexpectedly null

I've tried adding the following to the packages (both in a net452 and a net7 project):

  • id="Microsoft.Build" version="15.1.1012"
  • id="Microsoft.Build.Framework" version="15.1.1012"
  • id="Microsoft.Build.Runtime" version="15.1.1012"
  • id="Microsoft.Build.Tasks.Core" version="15.1.1012"
  • id="Microsoft.Build.Utilities.Core" version="15.1.1012"

Still get the same result.

I've also tried using the BuildManager like this:

var buildManager = new BuildManager();
buildManager.Build(new BuildParameters(),
                   new BuildRequestData(new ProjectInstance(CS_PROJ_FILE), 
                                        new[] {"Build"}));

I hit the same error after I installed:

Install-Package Microsoft.Build -Version 15.1.1012

But then I installed:

Install-Package Microsoft.Build.Utilities.Core -Version 15.1.1012

And things started working.

A little confusing...

I was pointed to this stackoverflow question by "dasMulli" at:

Project Class (Microsoft.Build.BuildEngine), I hit the same error after I installed: Install-Package Microsoft.Build -Version 15.1.​1012. But then I installed: Install-Package Microsoft.Build. In addition, NuGet also hosts a legacy assembly, Microsoft.Build.Engine, which is deprecated. There are several different versions of the MSBuild API, and for versions 15 and 16, there are two distinct forms of the assemblies in the NuGet packages, one compiled with the .NET Framework, and another compiled with .NET Core, which is a subset of the .NET Framework API surface.

There is apparently a new way to fix this problem, as described here and here.

Here's what worked for me:

  1. I deleted Microsoft.Build.dll, Microsoft.Build.Framework.dll, Microsoft.Build.Tasks.Core.dll and Microsoft.Build.Utilities.Core.dll (i.e., all Microsoft.Build .dll files) from my project's output folder.

  2. I deleted several Microsoft.Build NuGet packages from my project's references.

  3. I installed the Microsoft.Build.Locator NuGet package for my project.

  4. I added the following code to my program:

     // This needed after upgrading to Roslyn revision 34025, see these two links:

This fixed the exception listed by the OP and avoided the tons of compiler error messages about being unable to resolve all references.

Edit: More information here:

MSBuild Class (Microsoft.Build.Tasks), NET SDK is located for new SDK-style projects: the SDK contains .targets files with the targets and tasks for the new project system. There are  I'm trying to build a project using the classes in Microsoft.Build. The code is: var project = new ProjectInstance(CS_PROJ_FILE); project.Build(); However it's throwing the following exception:

Micrsoft provides a good link here

The trick is indeed to use nuget pacakges, and to specify ExcludeAssets=runtime to tell NuGet that the assemblies are needed only at build time, and shouldn't be copied to the output directory.

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  • Odd. I'll try again with a clean project.
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