I have an application loaded in my local environment. This is a codebase that I have inherited and have not gotten it to work at all. At this time, when I navigate to "http://test.myapp.com:75/" in my browser, I receive the following error:
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately. Parser Error Message: Could not load file or assembly 'Microsoft.ServiceModel.DomainServices.Hosting, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.
I have checked and verified that I have RIA Data Services loaded. I can see the files in C:\Program Files (x86)\Microsoft SDKs\RIA Services\v1.0\Libraries\Server. Interestingly, the assemblies in this directory are not loaded into my GAC. I've tried loading them into my GAC, however, I cannot drag the assemblies into C:\Windows\assembly and no error is shown when I try.
What am I doing wrong?
The Microsoft.ServiceModel.DomainServices.Hosting library is not part of the standard WCF RIA Services. You have to download and install the WCF RIA Services Toolkit seperately.
I also recommend reading WCF Extensibility – Configuring the Endpoint for WCF RIA Services.
I had the same problem , and solved.
The files "Microsoft.ServiceModel.DomainServices.Hosting.dll" in C:\Program Files (x86)\Microsoft SDKs\RIA Services\v1.0\Libraries\Server is the wrong one.
The right one is here
C:\Program Files (x86)\Microsoft SDKs\RIA Services\v1.0\Libraries\Server\SP2
I think this problem maybe caursed by the dll file version. the first one is old and the second one is new .
Setting your .NET version incorrectly in the application list can also create this issue.
来源：https://stackoverflow.com/questions/8028201/could-not-load-file-or-assembly-microsoft-servicemodel-domainservices-hosting