Could not load file or assembly System.Web.Http.WebHost after published to Azure web site

Question

I created a web project and it runs well in Visual studio. However, I got the following error after published it to azurewebsites. What can cause the issue?

Answer 1

I met the same problem and I resolved it by setting CopyLocal to true for the following libs:

System.Web.Http.dll
System.Web.Http.WebHost.dll
System.Net.Http.Formatting.dll

I must add that I use MVC4 and NET 4

Answer 2

This happened to me on VS2013(Update 5)/ASP.NET 4.5, under project type "Web Application" that includes MVC and Web API 2. Error happened right after creating the project and before adding any code. Adding the following configuration fix it for me. After resolving "System.Web.Helpers" issue two more similar errors surfaced for "System.Web.Mvc" and "System.Web.WebPages".

<runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-2.0.0.0" newVersion="2.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-5.0.0.0" newVersion="5.2.3.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
      </dependentAssembly>

Answer 3

In the case if "Copy Local" is already True, I find it sometimes to work if you remove the files where it has been published to and publish again.

For example if you're using IIS, remove the websites and the contents of the directory to which they are published to, and publish again.

There might be older versions of files at the destination, so to ensure you aren't using older versions, delete everything before publishing again.