Question

I have configured mini profiler with asp.net mvc application. I also want to profile my db so I hooked it with L2S datacontext as in this example.

It is working fine for some queries but on other queries I find null reference exception. When I attached the source code to debug I found out that

 internal void AddSqlTiming(SqlTiming stats)
        {
            Head.AddSqlTiming(stats);
        }

Head Property in above method is null in MiniProfiler.cs at line 198. Any idea why?

EDIT: Following method returns me the datacontext object

public static EvoletDataContext Get() 
        {
            var connection = ProfiledDbConnection.Get(new SqlConnection(ConfigurationManager.ConnectionStrings["evoletworksConnectionString"].ToString()));
            //var connection = new SqlConnection(ConfigurationManager.ConnectionStrings["evoletworksConnectionString"].ToString());
            //return new EvoletDataContext(connection);
            return DataContextUtils.CreateDataContext<EvoletDataContext>(connection);
        }

And below is the query on which miniprofiler crashes for the first time

public sysModule GetModuleHead(string actionName)
        {
            var val =  (from mod in db.sysModules
                        where
                        mod.ModuleActionResult.ToLower().Equals(actionName.ToLowerInvariant())
                    select mod).SingleOrDefault();
            return val;


        }

For more detail, please see this question as well. I tried but failed to reproduce problem in demo project.

Edit 2: Here is the stacktrace:

[NullReferenceException: Object reference not set to an instance of an object.]
   MvcMiniProfiler.MiniProfiler.AddSqlTiming(SqlTiming stats) in C:\Dev\mvc-mini-profiler\MvcMiniProfiler\MiniProfiler.cs:241
   MvcMiniProfiler.SqlTiming..ctor(DbCommand command, ExecuteType type, MiniProfiler profiler) in C:\Dev\mvc-mini-profiler\MvcMiniProfiler\SqlTiming.cs:66
   MvcMiniProfiler.SqlProfiler.ExecuteStartImpl(DbCommand command, ExecuteType type) in C:\Dev\mvc-mini-profiler\MvcMiniProfiler\SqlProfiler.cs:50
   MvcMiniProfiler.SqlProfilerExtensions.ExecuteStart(SqlProfiler sqlProfiler, DbCommand command, ExecuteType type) in C:\Dev\mvc-mini-profiler\MvcMiniProfiler\SqlProfiler.cs:95
   MvcMiniProfiler.Data.ProfiledDbCommand.ExecuteDbDataReader(CommandBehavior behavior) in C:\Dev\mvc-mini-profiler\MvcMiniProfiler\Data\ProfiledDbCommand.cs:149
   System.Data.Common.DbCommand.ExecuteReader() +12
   System.Data.Linq.SqlClient.SqlProvider.Execute(Expression query, QueryInfo queryInfo, IObjectReaderFactory factory, Object[] parentArgs, Object[] userArgs, ICompiledSubQuery[] subQueries, Object lastResult) +724
   System.Data.Linq.SqlClient.SqlProvider.ExecuteAll(Expression query, QueryInfo[] queryInfos, IObjectReaderFactory factory, Object[] userArguments, ICompiledSubQuery[] subQueries) +189
   System.Data.Linq.SqlClient.SqlProvider.System.Data.Linq.Provider.IProvider.Execute(Expression query) +659
   System.Data.Linq.DataQuery`1.System.Linq.IQueryProvider.Execute(Expression expression) +59
   System.Linq.Queryable.SingleOrDefault(IQueryable`1 source) +265
   UserManagement.Models.FilterRepository.GetModuleHead(String actionName) in D:\Evolet\UserManagement\UserManagement\Models\FilterRepository.cs:14
   UserManagement.Models.DummyAttrib.OnAuthorization(AuthorizationContext filterContext) in D:\Evolet\UserManagement\UserManagement\Models\Filters.cs:30
   Glimpse.Net.Plumbing.GlimpseAuthorizationFilter.OnAuthorization(AuthorizationContext filterContext) +157
   System.Web.Mvc.ControllerActionInvoker.InvokeAuthorizationFilters(ControllerContext controllerContext, IList`1 filters, ActionDescriptor actionDescriptor) +149
   System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +830
   System.Web.Mvc.Controller.ExecuteCore() +135
   System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +232
   System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +39
   System.Web.Mvc.<>c__DisplayClassb.<BeginProcessRequest>b__5() +68
   System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +44
   System.Web.Mvc.Async.<>c__DisplayClass8`1.<BeginSynchronous>b__7(IAsyncResult _) +42
   System.Web.Mvc.Async.WrappedAsyncResult`1.End() +140
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +54
   System.Web.Mvc.Async.AsyncResultWrapper.End(IAsyncResult asyncResult, Object tag) +40
   System.Web.Mvc.<>c__DisplayClasse.<EndProcessRequest>b__d() +61
   System.Web.Mvc.SecurityUtil.<GetCallInAppTrustThunk>b__0(Action f) +31
   System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +56
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +110
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +38
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +690
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +194

Answer 1

This used to happen if you had a ProfiledDbConnection in play and the actual profiler was set to null.

In general we avoid serving our internal consumers a ProfiledDbConnection if the current request is not profiled … this means everything is just a bit faster.

Unfortunately, this can be sometimes tricky to do with EF and L2S. To overcome this I just checked in a change that allows you to use the Profiling bespoke objects even if no profiler is in play.

Nonetheless, my recommendation remains that you should be using raw connections where possible when you are not profiling.