DLL Couldn't Be Loading Because of Binding Redirect

user_2258605 0
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I have a DLL project that uses the SendGrid Nuget package. The SendGrid package requires the Nuget package System.Net.Http 4.3.4. This DLL project I've then packaged into a Nuget package.

Now, I have a ASP.NET MVC project that includes my Nuget package. Because of dependency requirements installing it installs SendGrid, System.Net.Http, and other dependencies.

Now, when I have my web app try to send an email I got the following error.

System.IO.FileNotFoundException
HResult=0x80070002
Message=Could not load file or assembly 'System.Net.Http, Version=4.2.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.
Source=Bc3.Mail
StackTrace:
  at Bc3.Mail.MailHelper.SendMessage(SendGridMessage message) in C:\Code\Shared Libraries\Bc3.Mail\Bc3.Mail\MailHelper.cs:line 166
  at Bc3.Mail.MailHelper.SendMail(MailMessage mail) in C:\Code\Shared Libraries\Bc3.Mail\Bc3.Mail\MailHelper.cs:line 128
…

Now, I'm confused since I thought version 4.3.4 was installed. I checked the version of System.Net.Http in all my projects and it says it's version 4.2.0.0. Ok, I'm confused why it's showing 4.2 when I thought I installed 4.3.4. However, if 4.2 is referenced in my project how could it not find it?

Anyway, next I looked at my web.config file and saw this

<dependentAssembly>
    <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral"/>
    <bindingRedirect oldVersion="0.0.0.0-4.2.0.0" newVersion="4.2.0.0"/>
</dependentAssembly>

I don't know anything about these binding redirect. But I decided to remove this and everything worked fine.

So my question is why?

Thanks

assembly-binding-redirect asp.net-mvc c#
2 Answers

About binding redirects

Binding redirects allow the runtime to select alternative versions of a specific assembly. Binding redirects can be helpful because they reduce the strictness for binding to a specific version of an assembly. But, they can bring about conflicts.

https://docs.microsoft.com/en-us/dotnet/framework/configure-apps/redirect-assembly-versions

Binding redirect after adding SendGrid

I noticed that adding a NUGET reference to SendGrid inserted the following binding redirects

  <dependentAssembly>
    <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
    <bindingRedirect oldVersion="0.0.0.0-4.1.1.2" newVersion="4.1.1.2" />
  </dependentAssembly>

Creating a NUGET package that uses SendGrid

I created a simple class library project which references SendGrid and made a NUGET package. I placed this NUGET package in my private feeds folder and then referenced this NUGET package from another Framework project. The compiled .CONFIG file had the following binding redirect

<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-4.2.0.0" newVersion="4.2.0.0" />
      </dependentAssembly>

Possibility

My thoughts:

  1. The binding redirect that you are seeing in the web.config might have been brought about by an inadvertent reference to some other NUGET package
  2. Allow the compiler to generate binding redirects during the Build operation as opposed to manually adding binding redirects in the Web.config or app.config . The Project setting --> Application tab --> Auto-generate binding redirects should be checked.

Hope this helps.

user_29896550

It looks like something got messed up. The binding redirect would have been put there when any 2 of your nuget packages wanted different versions of Net.Http. Or you manually installed 4.2. This would make all references to a Net.Http use the 4.2 one instead.

So that is what is happening, except it seems you don't have Net.Http 4.2 in your project anymore. It seems this redirect was accidentally left behind somehow (maybe git or something locked the file when it was trying to change it?)

user_10792670
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