Question

I have an EDMX with an Agent, Client, Transaction and Form. Agent’s have Clients which have Transactions and Transactions have forms.

I want to use projection to get all of the entities for an agent at once to put in a hierarchichal treeview. The treeview needs to only show Transactions and Forms by the year selected.

My query in SQL would look something like this:

SELECT c.*, t.*, f.* FROM Client c
INNER JOIN Client_Bucket_Client cbc on cbc.Client_GUID = c.Client_GUID
INNER JOIN Agent_Client_Bucket acb on acb.Client_Bucket_GUID = cbc.Client_Bucket_GUID
LEFT OUTER JOIN [Transaction] t on t.Client_GUID = c.Client_GUID
LEFT OUTER JOIN [Form] f on f.Transaction_GUID = t.Transaction_GUID
WHERE f.Year = 2011 AND t.Year = 2011 AND acb.Agent_GUID = 'A29B6E94-3F1B-E011-B68A-001F290A2D4A'
ORDER BY c.Last_Change_Date desc, c.File_Under

Right now my linq looks like this:

var clients = from client in ObjectContext.Clients
                  join cbc in ObjectContext.Client_Bucket_Client on client.Client_GUID equals cbc.Client_GUID
                  join acb in ObjectContext.Agent_Client_Bucket on cbc.Client_Bucket_GUID equals acb.Client_Bucket_GUID
                  where acb.Agent_GUID == agentGuid
                  orderby client.Last_Change_Date descending, client.File_Under
                  select client;

    var clientInfos =
        from c in clients
        select new
        {
            Client = c,
            TransactionInfos = ObjectContext.Transactions
                .Where(t => t.Client_GUID == c.Client_GUID && t.Year == year)
                .Select(t => new
                {
                    Transaction = t,
                    ToAttach = ObjectContext.Forms.Where(f => f.Transaction_GUID == t.Transaction_GUID && f.Year == year)
                })
        };

    // Looping over this query will hit the database *once*
    foreach (var info in clientInfos)
    {
        foreach (var transactionInfo in info.TransactionInfos)
        {
            transactionInfo.Transaction.Forms.Attach(transactionInfo.ToAttach);
        }

        var tt = info.TransactionInfos.ToList(); //.Select(t => t.Transaction);

        var trans = tt.Select(t => t.Transaction);

        info.Client.Transactions.Attach(trans);
    }

    // Return a queryable object; constructing a new query from this will hit the database one more time
    return clients;

But I get an error :

Load operation failed for query ‘GetTopLevelData’. An error occurred while executing the command definition. See the inner exception for details. Inner exception message: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.

Here is the Stack Trace:

at System.Data.EntityClient.EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand, CommandBehavior behavior) at System.Data.Objects.Internal.ObjectQueryExecutionPlan.Execute[TResultType](ObjectContext context, ObjectParameterCollection parameterValues) at System.Data.Objects.ObjectQuery1.GetResults(Nullable1 forMergeOption) at System.Data.Objects.ObjectQuery1.System.Collections.Generic.IEnumerable<T>.GetEnumerator() at RealForms.Web.Data.RealFormsService.GetTopLevelData(Guid agentGuid, Int32 year) in C:\Users\Bryan\Documents\Visual Studio 2010\Projects\RealForms\RealForms.Web.Data\RealFormsService.cs:line 590 at GetTopLevelData(DomainService , Object[] ) at System.ServiceModel.DomainServices.Server.ReflectionDomainServiceDescriptionProvider.ReflectionDomainOperationEntry.Invoke(DomainService domainService, Object[] parameters) at System.ServiceModel.DomainServices.Server.DomainOperationEntry.Invoke(DomainService domainService, Object[] parameters, Int32& totalCount) at System.ServiceModel.DomainServices.Server.DomainService.Query(QueryDescription queryDescription, IEnumerable1& validationErrors, Int32& totalCount) at System.ServiceModel.DomainServices.Hosting.QueryProcessor.Process[TEntity](DomainService domainService, DomainOperationEntry queryOperation, Object[] parameters, ServiceQuery serviceQuery, IEnumerable1& validationErrors, Int32& totalCount) at System.ServiceModel.DomainServices.Hosting.QueryOperationBehavior1.QueryOperationInvoker.InvokeCore(Object instance, Object[] inputs, Object[]& outputs)

I’m finding that this error only occurs on certain data. It seems something is null somehwere??

Answer 1

If you want to achieve JOIN in SQL why don’t you use JOIN in LINQ?

http://msdn.microsoft.com/en-us/library/bb534675.aspx

This is how you might join clients with transactions:

var clientTransactions = clients
       .Join(ObjectContext.Transactions, c => c.Client_GUID, t => t.Client_GUID, 
                    (c,t) => new {Client = c, Transaction = t});

It’s hard to predict which SQL query produces your linq so I would prefer using this syntax for JOIN.

P.S.: You’re getting a timeout – it’s definitely depends on data, especially on data volume. Try profiling which queries your LINQ sends to SQL server.