SharePoint 2010 Webservice: URL could not be found

Question

Always getting the following error while trying to create a spsite-object:

The Web application "http://myApplicationURL/" at could not be found. Verify that you have typed the URL correctly. If the URL should be serving existing content, the system administrator may need to add a new request URL mapping to the intended application.

The webservice should access the local SharePoint-Application which does work in a browser. First it seems like a common problem, but tried all the web-suggested solutions:

• compiling as "any platform" or x64
• using .Net 3.5
• starting as farm administrator / don't start as farm administrator
• trying the published version of the webservice instead of debugging in VS2010
• modifying: regedit DisableLoopBackCheck to 1, means I'm able to log in locally to the application/the other applications
• tried to access a different application on the same server -> same problem
• used elevated privileges
• starting VS2010 with "ADMIN"-Privileges
• adding the starting user (is farm admin) to WSS_ADMIN_WPG windows user group
• users are fully privileged on SQL content database
• users are site collection as well

what else could be wrong?

Here some code, it's simple as that:

class Program
{
    static void Main(string[] args)
    {
        using (SPSite site = new SPSite("http://test-sharepoint.myApp.local"))
        {

        }
    }
}

Answer 1

I just had to set the AppPool for the WebService: I set it to the same AppPool that the SharePoint application had. It started to work immediately - even if the original AppPool does have the same configurations as the SP2010-AppPool has...

To debug the WebService, just connect the VisualStudio-Debugger to the w3wp.exe-process.

Answer 2

Excerpt from Stefan GoBner's Blog:

Here are the most common reasons this error can occur:

1. The code is executed on a different machine - The SharePoint object model (except the Client API) requires to be run on the SharePoint server itself. It is not possible to run the application on a server which is not within the same SharePoint farm the code is trying to access.
   1. Insufficient Rights on the site collection - The code is executed in context of an account which does not have read permission on the site collection
   2. Incorrect Url being used - Verify that the site works correct in a browser and double check that the server is correct registered in the AAM settings
   3. Incorrect bitness - The SharePoint object model needs to be executed with the same bitness as the operating system. That means you cannot use the SharePoint object model in a 32-bit application if the Operating System and SharePoint are installed as 64-bit version. Ensure to compile the project using the correct bitness (64-bit on a 64-bit machine vs. 32-bit on a 32-bit machine)
   4. Incorrect .NET framework version - Ensure that the project is configured to use .NET 3.5. .NET 4.0 cannot be used with the current versions of SharePoint