The Issue:

After I had updated my .Net Core on my developer machine to a newer version I went to debug a web application I had and received this error:

Could not load file or assembly 'DotNetOpenAuth.Core, Version=4.1.0.0, Culture=neutral, PublicKeyToken=2780ccd10d57b246' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

The Problem:

Here is what I had in my config prior to the update install:

[sourcecode]
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentAssembly>
<assemblyIdentity name="DotNetOpenAuth.Core" publicKeyToken="2780ccd10d57b246" />
<bindingRedirect oldVersion="1.0.0.0-4.0.0.0" newVersion="4.1.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="DotNetOpenAuth.AspNet" publicKeyToken="2780ccd10d57b246" />
<bindingRedirect oldVersion="1.0.0.0-4.0.0.0" newVersion="4.1.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="EntityFramework" publicKeyToken="b77a5c561934e089" />
<bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
</dependentAssembly>
</assemblyBinding>
</runtime>
[/sourcecode]

I had outdated references in my config file.

The Solution:

Ensure your references get updated after you update your development environment.

Here is what I updated to:

[sourcecode]
<runtime>
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
<dependentAssembly>
<assemblyIdentity name="DotNetOpenAuth.AspNet" publicKeyToken="2780ccd10d57b246" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-4.3.0.0" newVersion="4.3.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="DotNetOpenAuth.Core" publicKeyToken="2780ccd10d57b246" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-4.3.0.0" newVersion="4.3.0.0" />
</dependentAssembly>
<dependentAssembly>
<assemblyIdentity name="EntityFramework" publicKeyToken="b77a5c561934e089" />
<bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0" />
</dependentAssembly>
</assemblyBinding>
</runtime>
[/sourcecode]

Hope that helps. Questions are always welcome.