Question

When I start the application from Visual Studio 2010 the following error shows up:

Value cannot be null.\r\nParameter name: username

I can see this error in Global.asax.cs in the parameter sender of this method:

    void Application_Error(object sender, EventArgs e)
    {
    }

The problem is that I’m not using username anywhere and my web.config

    <configuration>
      <connectionStrings>
        <add name="MYSQL"
             connectionString="Driver={MySQL ODBC 5.2w Driver};Server=server_name;Database=database_name;uid=my_user_id;pwd=my_pwd"
             providerName="System.Data.Odbc"/>
      </connectionStrings>
      <system.web>
         <compilation debug="true" targetFramework="4.0" />
      </system.web>
  </configuration>

Any help will be welcome.

EDIT:

More information:

What I can see is:

sender.base.Profile.base.base.Session = '((System.Web.HttpApplication)(sender)).Session' threw an exception of type 'System.Web.HttpException' 

and

sender.Profile.base.LastActivityDate = '((System.Web.Profile.ProfileBase)(((ASP.global_asax)(sender)).Profile)).LastAct‌​ivityDate' threw an exception of type 'System.ArgumentNullException' 

and

sender.Profile.base.LastActivityDate.base = {"Value cannot be null.\r\nParameter name: username"}

EDIT

This code works without any problem, and also I can execute queries.

    void Application_Start(object sender, EventArgs e)
    {
        string ConnStr = System.Configuration.ConfigurationManager.ConnectionStrings["MYSQL"].ConnectionString;
        OdbcConnection con = new OdbcConnection(ConnStr);
        con.Open();
        con.Close();
     }

Answer 1

For some reason this error only happens when I run the application from Visual Studio and not when it is deployed in IIS.

Thank you for your help!