ELMAH - Distinction between Application and Source fields in ELMAH_Error table

Question

ELMAH's creator has provided a table creation script to record exceptions:

CREATE TABLE [dbo].[ELMAH_Error]
(
    [ErrorId]     UNIQUEIDENTIFIER NOT NULL,
    [Application] NVARCHAR(60)  COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
    [Host]        NVARCHAR(50)  COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
    [Type]        NVARCHAR(100) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
    [Source]      NVARCHAR(60)  COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
    [Message]     NVARCHAR(500) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
    [User]        NVARCHAR(50)  COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
    [StatusCode]  INT NOT NULL,
    [TimeUtc]     DATETIME NOT NULL,
    [Sequence]    INT IDENTITY (1, 1) NOT NULL,
    [AllXml]      NVARCHAR(MAX) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL 
) 

Can anyone tell me when Application and Source should be different? Application is set via the errorLog element's applicationName attribute:

<errorLog type="Elmah.SqlErrorLog, Elmah" connectionStringName="elmah-sqlserver" applicationName="My Cool App"/>

What is Source? Name of the executing assembly?

Answer 1

That should be the assembly name of the assembly containing the class that threw the exception.

Example:

System.Web.HttpException (0x80004005): The controller for path '/scripts/knockout-custombindings' was not found or does not implement IController.
   at System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType)
   at System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName)
   at System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory)
   at System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state)
   at System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state)
   at System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

In this case, System.Web.Mvc.dll is asked for a file which does not exist and does not map to a MVC controller. In this case Source will be equal to System.Web.Mvc.