LLBLGen.com Forums Linq to LLBLGen Pro feed

Dynamic Query Execution Using Predicate Builder by daelmo

daelmo — Fri, 03 Sep 2010 21:44:42 GMT

carni4 wrote:

Since the above code works just fine (and runs just a single SQL statement on the server, without any client side filtering), I'm unclear as to why I should consider using the Predicate Builder at the moment. Thanks in advance for the advice.

You can take advantage of PredicateBuilder (IMHO) if you need to isolate the predicate for any reason (you receive the predicate in a fetch method, or you need to pass the predicate over the wire, or your method does know nothing about the filter parameters and it have to call other method to obtain the predicate). In such cases you could consider use it. Consider the following code:

Code:

public void GetCustomersUsingPredicateBuilder()
{
    var predicate = PredicateBuilder.Null<CustomerEntity>();

    using(DataAccessAdapter adapter = new DataAccessAdapter())
    {
        LinqMetaData metaData = new LinqMetaData(adapter);
        predicate = predicate.Or(c => c.City == "London");
        predicate = predicate.Or(c => c.City == "Paris");

        var q = metaData.Customer.Where(predicate);

        foreach(var v in q)
        {
            Assert.IsTrue((v.City == "London") || (v.City == "Paris"));
        }
    }
}

Note that predicate is independent, you use it just in the metaData.Customer.Where(predicate) line.

Deleteing from IQueryable<T> by daelmo

daelmo — Fri, 03 Sep 2010 21:32:27 GMT

No possible, at least not built in (I suppose you can write code to translate a linq expression to a predicateexpression) . LINQ2LLBL is just for fetching. So if you don't want to fetch, you need to write the predicate with LLBLGen api classes (PredicateExpression) and use the adapter.DeleteMulti method.

Deleteing from IQueryable<T> by rboarman

rboarman — Fri, 03 Sep 2010 20:39:36 GMT

Given an IQueryable<T>, how can I delete the data without fetching the records via ToList()?

For example:

Code:

var requests = from r in Repository.For<RequestEntity>()
                               where r.ClientId == clientId
                               select r;

dbAdapter.Delete (requests); <== or something like this

Thanks,

Rick

Dynamic Query Execution Using Predicate Builder by carni4

carni4 — Fri, 03 Sep 2010 15:04:55 GMT

Hi there. Is there any advantage to using the Predicate Builder over say, doing something like the following?

Code:


using (DataAccessAdapter adapter = new DataAccessAdapter())
            {
                LinqMetaData meta = new LinqMetaData(adapter);

                var involvedParties = from ip in meta.InvolvedParty
                                                       select ip;

                if (timeZoneID.HasValue)
                    involvedParties = involvedParties.Where(ip => ip.Contact.TimeZoneID == timeZoneID.Value);

                if (stateID.HasValue)
                    involvedParties = involvedParties.Where(ip => ip.Contact.City.CountryStateID == stateID.Value);

                if (specialtyID.HasValue)
                    involvedParties = involvedParties.Where(ip => ip.SpecialtyID == specialtyID.Value);

                if (!string.IsNullOrEmpty(zipCode))
                    involvedParties = involvedParties.Where(ip => ip.Contact.ZipCode == zipCode);

                var data = from ip in involvedParties
                           select new
                           {
                               ip.InvolvedPartyID,
                               ip.Contact.CompanyName,
                               ip.IsAutoApprovedClient
                           };

                return data.ToList();
            }

Linq to LLBLGen Pro, ServerMode and caching by BaerlinEDV

BaerlinEDV — Thu, 02 Sep 2010 11:45:42 GMT

Wow, now that's a fast answer.

Thanks for pointing that out, so we were thinking into the wrong direction, sorry for that.

Linq to LLBLGen Pro, ServerMode and caching by Otis

Otis — Thu, 02 Sep 2010 11:37:32 GMT

llblgen pro doesn't cache query results, because we believe that that should be left to the application or the database. So if you see rows not being re-read, it's likely the controls you're using aren't re-issuing a fetch.

Linq to LLBLGen Pro, ServerMode and caching by BaerlinEDV

BaerlinEDV — Thu, 02 Sep 2010 11:31:37 GMT

Hello there,

we're running a multi-user environment with several tables that are permanently growing. One of those tables can recieve updates (new rows, edited rows) every few minutes, so we thought using Linq to LLBLGen Pro, together with the DevExpress' XtraGrid's ServerMode exactly fit our requirements, but noticed that rows are only fetched the first time they're addressed.

Is there a way to force the datasource to fetch rows everytime a row is accessed instead of caching already fetched rows? (Because we couldn't find one yet).

Thanks in advance,
best regards
Phil

Possible bug with Any() by JMuller

JMuller — Tue, 31 Aug 2010 15:31:00 GMT

"hides in a corner"

I did update the LinqSupportClasses.DLL, only at the wrong place

I was calling a webservice in a website, who was then calling a project. I updated the DLL in the project, but after updating in the website, it worked!

Sorry for bothering.

Possible bug with Any() by Otis

Otis — Tue, 31 Aug 2010 15:00:33 GMT

please post the runtime library build nr and linq library build nr. See: http://www.llblgen.com/tinyforum/Messages.aspx?ThreadID=12769

i.o.w.: make sure you're using the latest build

Possible bug with Any() by JMuller

JMuller — Tue, 31 Aug 2010 14:58:14 GMT

Hi,

Im trying to execute the following query:

Code:



using (DataAccessAdapter adapter = new DataAccessAdapter())
{
    LinqMetaData metaData = new LinqMetaData(adapter);

            
    var customers = from nv in metaData.Customer
            where ((nv.Emailaddress == klantRow.Emailaddress &&
                         nv.LastName == klantRow.Emailaddress ) ||
                    (nv.Postalcode == klantRow.Postalcode &&
                     nv.HouseNumber == klantRow.HouseNumber &&
                     nv.LastName == klantRow.LastName )) &&
                     nv.CustomerId != klantRow.CustomerId 
     select nv;
    
         if (klanten.Any())
    {
        //TODO
    }
}

but this returns the following error:

Code:


An exception was caught during the execution of a retrieval query: 
The multi-part identifier \"LPA_L1.Emailaddress \" could not be bound.
And alot more fields could not be bound.

The generated query:

Code:



SELECT TOP(@top6) CASE WHEN EXISTS (
    SELECT [LPA_L1].[CustomerId] FROM (
        [LPA_L1].[Emailaddress ] AS [Emailaddress]
        FROM [KNM].[dbo].[Customers] [LPLA_1]  
        WHERE ( ( ( ( 
            ( [LPA_L1].[Emailaddress] = @Emailaddress1) AND
            ( [LPA_L1].[LastName] = @LastName2)) OR
             ( ( ( [LPA_L1].[Postalcode] = @Postalcode3) AND 
             ( [LPA_L1].[HouseNumber] = @HouseNumber4)) AND 
             ( [LPA_L1].[LastName] = @LastName5))) AND 
             ( [LPA_L1].[CustomerId] <> @CustomerId6)))) [LPA_L1]) 
             THEN 1 ELSE 0 END AS [LPFA_1] 
        FROM [KNM].[dbo].[Klanten] [LPLA_1]

Seems to me that there's a bug in the alias names.

I tried to use Count instead Any, which worked fine btw.

Greetings.

This happens with LBLL 2.6 Final