Adding new MVC/Razor items fails throwing an error about hostpolicy.dll

This post was most recently updated on July 31st, 2022.

This article describes how to fix the error “There was an error running the selected code generator: ‘Failed to load the dll from \bin\Debug\netcoreapp\win-x86\hostpolicy.dll, HRESULT: 0x800700C1 An error occurred while loading required library hostpolicy.dll'” when you’re adding a new scaffolded item (such as a Razor page or ASP.NET Core MVC Controller) in Visual Studio.

Description

Imagine this: You’re developing your run-of-the-mill, basic, everyday ASP.NET Core web application. You need to add a new scaffolded item – that is, something like a Razor page or an MVC controller.

This will result in an error somewhat like the below:

There was an error running the selected code generator:
'Failed to load the dll from [projectpath]\bin\Debug\netcoreapp\win-x86\hostpolicy.dll, HRESULT: 0x800700C1

An error occurred while loading required library hostpolicy.dll from ...

Solution

We have, in fact, seen this one before! A different context, similar error – so we actually know how to fix it!

For the other post (about a similar error with EF Core), see the post below. Even though it describes a fix to an issue that arises when running Update-Database, the underlying error is in fact the same that causes the error “There was an error running the selected code generator: (HRESULT: 0x800700C1)” for us here.

Essentially – modify your project file to have a RuntimeIdentifiers -node instead of RuntimeIdentifier. See below for more details:

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Antti K. Koskela

Developer / Speaker / Consultant at Koskila / Precio Fishbone / Norppandalotti Software Co / Alter - Experience Ideas Ltd

Antti Koskela is a proud digital native nomadic millennial full stack developer (is that enough funny buzzwords? That's definitely enough funny buzzwords!), who works as Solutions Architect for Precio Fishbone, building delightful Digital Workplaces.

He's been a developer from 2004 (starting with PHP and Java), and he's been working on .NET projects, Azure, Office 365, SharePoint and a lot of other stuff. He's also Microsoft MVP for Office Development.

This is his personal professional (e.g. professional, but definitely personal) blog.

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