Error Debugging MVC 3 after Publish - asp.net-mvc-3

Question

I had done one publish to my MVC application. After that, I cannot debug it anymore!
This is the error. It seems that my visual studio web server is loading machine.config
Server Error in '/' Application.
Configuration 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: The connection name 'LocalSqlServer' was not found in the applications configuration or the connection string is empty.
Source Error:
Line 255:
Line 256:
Source File: C:\Windows\Microsoft.NET\Framework\v4.0.30319\Config\machine.config Line: 257
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.237
This is how my web.config looks like, and there is nothing in my code that uses ASP.Net Membership as my authentication mode is "Windows".
I did manage to run it again in Visual Studio once, after I set the build mode from "Release" to "Debug" vice versa, but after I published again today.. The problem came back.
<configuration>
<connectionStrings>
<clear/>
<add name="ApplicationServices" connectionString="Data Source=SCG1SQL-64;Initial Catalog=Metallurgy;Integrated Security=True"
providerName="System.Data.SqlClient" />
<add name="mandb100ConnectionString" connectionString="Data Source=scg1sql-64;Initial Catalog=mandb100;Integrated Security=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
<appSettings>
<add key="webpages:Version" value="1.0.0.0" />
<add key="ClientValidationEnabled" value="true" />
<add key="UnobtrusiveJavaScriptEnabled" value="true" />
</appSettings>
<system.web>
<authentication mode="Windows"/>
<authorization>
<deny users="?" />
</authorization>
</system.web>
</configuration>

Answer 1

Well, it is using the machine.config. There is a hierarchy of configuration. In other words, if you don't explicitly specify (or remove or clear) in your web.config, the base defaults will be pulled from the machine.config.
What your ASP.NET application will do is look for a web.config in the current directory for configuration. If that isn't found, or the desired configuration isn't found, it'll look to the application's web.config. Then for defaults, or uncleared or nonremoved items it'll also pull configuration from the machine.config.
But to the problem. What your error message is saying is that it can't find the LocalSqlServer connection string name anywhere. Are you sure that conn string name exists in your web.config?
Edit: Check your web.release.config file. You can find it in your Solution Explorer if you drop down the web.config file. Does that perhaps contain LocalSqlServer connection string?

Answer 2

This link might be of help: http://msdn.microsoft.com/en-us/library/webmatrix.webdata.preapplicationstartcode(v=vs.99).aspx
That's how I solved my problem. Apparently, this WebMatrix SimpleMembership is enabled by default. So I added this line in my web.config, and the problem disappeared!!!
<add key="enableSimpleMembership" value="false"/>

Answer 3

I know this is an old post, and as both these answers are correct to point you in the right direction to solve the issue, I'd like to add another solution if it might help anyone.
In my application an error occurred after I used the "Add Deployable Dependencies..." item in Solution Explorer, project context menu (right click on a project). This added a directory called _bin_deployableAssemblies with dlls needed to deploy your application on a server if it doesn't have some of them added to GAC. The dlls in the _bin_deployableAssemblies are copied to the bin directory of your application.
There were two dlls of interest that I wasn't using WebMatrix.Data and WebMatrix.WebData. Their presence in the bin directory of my application somehow messes the default membership provider resolving (correct me if I'm wrong, or add an explanation to what really happens :) ). The solution was to simply remove the offending dlls from the bin directory and from the _bin_deployableAssemblies as well.