Configuration Builders - Unable to load assembly - .Net Framework

Question

I am using file based User Secrets within my .Net Framework WebAPI and all is working fine with the AppSettings section of the web.config as per below

<configuration>
  <configSections>
    <section name="configBuilders" type="System.Configuration.ConfigurationBuildersSection, System.Configuration, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" restartOnExternalChanges="false" requirePermission="false" />
  </configSections>
  <configBuilders>
    <builders>
      <add name="Secrets" userSecretsFile="MySecretsFile.xml" type="Microsoft.Configuration.ConfigurationBuilders.UserSecretsConfigBuilder, Microsoft.Configuration.ConfigurationBuilders.UserSecrets, Version=1.0.0.0, Culture=neutral" />
    </builders>
  </configBuilders>
  <appSettings  configBuilders="Secrets">
    <add key="mysetting1" value="(default)" />
    <add key="mysetting2" value="(default)" />
  </appSettings>
</configuration>

However, I now need to add same for connectionStrings for EF connections and the following entries are in the web.config below

<connectionStrings configBuilders="Secrets">
  <add name="Entities" connectionString="A" providerName="System.Data.EntityClient" />
</connectionStrings>

When I run the app (in Visual Studio) I get the following error showing that the ConfigurationBuilders is having issues finding something.... but I don'k know what ... thing is, all the appSettings and configurationStrings are loading as expected.

If I remove the configBuilders="Secrets", then the error does not show.

So what am I missing, how can I find out what is it trying to load, but cannot find.

score 1 · Answer 1 · edited May 27 '21 at 08:08

I've spent two days trying to fix a similar issue. I've tried to install Sitecore 10.1 locally and it threw such an error.

I've also got a similar error when I decided to create a new project in Visual Studio and added configuration builders. For some reason, the dlls were not visible, but when I removed configuration builders and tried with Type.GetType in Global.asax it loaded assembly correctly.

So it seems that it can't correctly find an assembly when resolving configuration builders. I've tried to paste dlls in multiple places. I also added it to the GAC, but no luck. It could be related to this comment https://github.com/aspnet/MicrosoftConfigurationBuilders/issues/129#issuecomment-628247237 They are doing some kind of magic to make configuration builders work.

So after two days I've found this article https://learn.microsoft.com/en-us/dotnet/framework/configure-apps/file-schema/runtime/probing-element and added element like that

<runtime>
  <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
    <probing privatePath="bin"/>
    ...

I literally pointed to the bin folder. And worked.

score 0 · Answer 2 · answered Aug 02 '20 at 07:47

It does say which assembly loading you are having problem with. Have you verified your project actually correctly references Microsoft.Configuration.ConfigurationBuilders.UserSecrets? Verify the version number, is it 1.0.0.0. Easiest to verify by referencing types from that assembly directly in code. If compiler accepts this then likely runtime will as well.

If the obvious check didn't help then resolve to usual assembly loading troubleshooting. That is fuslogvw.exe/The Assembly Binding Log Viewer:

The Assembly Binding Log Viewer displays details for assembly binds. This information helps you diagnose why the .NET Framework cannot locate an assembly at run time. These failures are usually the result of an assembly deployed to the wrong location, a native image that is no longer valid, or a mismatch in version numbers or cultures. The common language runtime's failure to locate an assembly typically shows up as a TypeLoadException in your application.

(documentation)

Configuration Builders - Unable to load assembly - .Net Framework

2 Answers2