How to track what adds a 'DefaultConnection

I have a weird problem - I have noticed that after web deployment of my MVC app, a new connection string is added to web.config file.

<add name="DefaultConnection" connectionString="DefaultConnection_ConnectionString" providerName="System.Data.SqlClient" />

I have no idea where it comes from, something adds it automatically.

Here is my web.config file after publishing

  <?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
</configSections>
  <connectionStrings>
    <add name="AuditDbContext" connectionString="[An Azure connection string]" providerName="System.Data.SqlClient" />
       <add name="DefaultConnection" connectionString="DefaultConnection_ConnectionString" providerName="System.Data.SqlClient" />
  </connectionStrings>
  <appSettings>
    <add key="webpages:Version" value="3.0.0.0" />
    <add key="webpages:Enabled" value="false" />
    <add key="ClientValidationEnabled" value="true" />
    <add key="UnobtrusiveJavaScriptEnabled" value="true" />
    <add key="AuditingLevelModifier" value="0" />
    <add key="AuditingMode" value="DatabaseAndLogger" />
    <add key="IgnoreSslPolicyErrors" value="true" />
  </appSettings>
  <system.web>
    <compilation targetFramework="4.6" />
    <httpRuntime targetFramework="4.5.2" maxRequestLength="512000" />
     <httpCookies httpOnlyCookies="true" requireSSL="true" lockItem="true" />
    <httpModules>
      <add name="ApplicationInsightsWebTracking" type="Microsoft.ApplicationInsights.Web.ApplicationInsightsHttpModule, Microsoft.AI.Web" />
    </httpModules>
    <customErrors mode="Off" />
  </system.web>
  <system.webServer>
    <httpProtocol>
      <customHeaders>
        <add name="Strict-Transport-Security" value="max-age=16070400; includeSubDomains" />
      </customHeaders>
    </httpProtocol>
    <security>
      <requestFiltering>
        <requestLimits maxAllowedContentLength="314572800" />
      </requestFiltering>
    </security>
    <modules>
      <remove name="ApplicationInsightsWebTracking" />
      <add name="ApplicationInsightsWebTracking" type="Microsoft.ApplicationInsights.Web.ApplicationInsightsHttpModule, Microsoft.AI.Web" preCondition="managedHandler" />
    </modules>
    <validation validateIntegratedModeConfiguration="false" />
  <handlers>
      <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
      <remove name="OPTIONSVerbHandler" />
      <remove name="TRACEVerbHandler" />
      <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="*" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
    </handlers>
  </system.webServer>
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Owin.Security" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-3.0.1.0" newVersion="3.0.1.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Owin.Security.OAuth" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-3.0.1.0" newVersion="3.0.1.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Owin.Security.Cookies" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-3.0.1.0" newVersion="3.0.1.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.Owin" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-3.0.1.0" newVersion="3.0.1.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Newtonsoft.Json" culture="neutral" publicKeyToken="30ad4fe6b2a6aeed" />
        <bindingRedirect oldVersion="0.0.0.0-10.0.0.0" newVersion="10.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Optimization" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-1.1.0.0" newVersion="1.1.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="WebGrease" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="0.0.0.0-1.5.2.14234" newVersion="1.5.2.14234" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Antlr3.Runtime" publicKeyToken="eb42632606e9261f" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-3.5.0.2" newVersion="3.5.0.2" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Http" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Net.Http.Formatting" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Helpers" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.WebPages" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="3.0.0.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Mvc" publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-5.2.3.0" newVersion="5.2.3.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.IdentityModel.Tokens" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-5.1.2.0" newVersion="5.1.2.0" />
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="Microsoft.IdentityModel.Logging" publicKeyToken="31bf3856ad364e35" culture="neutral" />
        <bindingRedirect oldVersion="0.0.0.0-1.1.3.0" newVersion="1.1.3.0" />
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
  <entityFramework>
    <defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework" />
    <providers>
      <provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" />
    </providers>
  </entityFramework>

  <system.codedom>
    <compilers>
      <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:6 /nowarn:1659;1699;1701" />
      <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=1.0.3.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:14 /nowarn:41008 /define:_MYTYPE=\&quot;Web\&quot; /optionInfer+" />
    </compilers>
  </system.codedom>
  <log4net>
    <appender name="RollingFileAppender" type="log4net.Appender.RollingFileAppender">
      <file value="C:\Logs\Portal.log" />
      <encoding value="utf-8" />
      <appendToFile value="true" />
      <rollingStyle value="Date" />
      <datePattern value="dd.MM.yyyy'.log'" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date %level [%thread] %type.%method - %message%n" />
      </layout>
    </appender>
    <appender name="AuditTrailAppender" type="log4net.Appender.RollingFileAppender">
      <file value="C:\Logs\AuditTrail.log" />
      <encoding value="utf-8" />
      <appendToFile value="true" />
      <rollingStyle value="Date" />
      <datePattern value="dd.MM.yyyy'.log'" />

      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date %level [%thread] %type.%method - %message%n" />
      </layout>
    </appender>
    <appender name="TraceAppender" type="log4net.Appender.TraceAppender">
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date %level [%thread] %type.%method - %message%n" />
      </layout>
    </appender>
    <logger name="AuditTrailLogger" additivity="false">
      <level value="ALL" />
      <appender-ref ref="AuditTrailAppender" />
    </logger>
    <root>
      <level value="Debug" />
      <!-- If the following line is not included the log file 
      will not be created even if log4net is configured with this file. -->
      <appender-ref ref="RollingFileAppender" />
      <appender-ref ref="TraceAppender" />
    </root>
  </log4net>
</configuration>

I believe the only component of this web app which uses a connection string is Auditing module - EF is set to use another connection string (and it works) public AuditingContext() : base("name=AuditDbContext")

I am really puzzled where does it come from - especially that last night I had some weird errors related to this connection string. Basically, I noticed that it gets added when I started getting this error

Format of the initialization string does not conform to specification starting at index 0

At application startup - and when I removed the DefaultConnection, the error changed to a 'Network-related or instance-specific error occurred while establishing a connection to SQL Server.'

Anyway - how do I track where does it come from?

Cheers!

Ok, I've figured it out.

My pubxml profile adds it - look at these lines.

<ItemGroup>
    <MSDeployParameterValue Include="$(DeployParameterPrefix)AuditDbContext-Web.config Connection String" />
    <MSDeployParameterValue Include="$(DeployParameterPrefix)DefaultConnection-Web.config Connection String">
      <UpdateDestWebConfig>False</UpdateDestWebConfig>
    </MSDeployParameterValue>
  </ItemGroup>
  <ItemGroup>
    <_ConnectionStringsToInsert Include="DefaultConnection" />
  </ItemGroup>

I suppose it is being added because of the default code related to authorization, e.g.

app.CreatePerOwinContext(ApplicationDbContext.Create); in Startup

and

public ApplicationDbContext() : base("DefaultConnection", throwIfV1Schema: false) in IdentityModel class

Which leads me to more questions (why does it sometimes work!?), but that is out of scope of this question.