Question

LINQ to SQL, can you pass a query to another method

Asked by: yami_rider

I am not quite sure if this can be done and likewise not quite sure that it should be done, given the DataContext likes to work atomically.

I have a data access layer class that I will use LINQ to SQL to query my SQL 2005 database, so the code looks something like this:
            //attempt to use LiNQ here
            using (Outbound.dcCaseDataContext db = new Outbound.dcCaseDataContext())
            {
                var query = from cases in db.tblCases select cases;
                //--> Call method here pass in query
            }

I want to call a method and pass in the query the method will do some more work with regards to mapping and other business processes. My thought is the method might look like this:

 public IQueryable<T> SomeMethod<T>(IQueryable<T> dbSupportCases)
        {
            //Do some work
            return dbSupportCases;
        }

My main worry here is with the DataContext object.  As well as proper design. The reason I need to pass in the query to another class is I have a business layer that needs to perform some mapping and I want to ensure separation of concerns.

Any guidence would be appreciated I have looked at a few blog sites such as http://www.west-wind.com/WebLog/posts/159522.aspx and other ones, but I am not quite sure it is what I am trying to do.

Thank you

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Asked On
2009-09-25 at 18:52:27ID24763501
Tags

LINQ .NET C#

Topics

C# Programming Language

,

Language Integrated Query - LINQ

Participating Experts
2
Points
500
Comments
3

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Answers

 

by: daryalPosted on 2009-09-25 at 23:21:54ID: 25428941

Hello,
In my opinion, what you are trying to do is against seperation of layers. You should complete all db related jobs in data access layer, and just send the data to business layer for processing. If you are sending something that will not be directly used in business layer, it is not a good practice.
I can not think about a good practice in where you need your db query in business layer, maybe you should check your design.

 

by: naspinskiPosted on 2009-09-26 at 00:07:43ID: 25429052

You can pass in queries, depending on what your query is returning, you just have to adjust your method, most of the time is an IEnumerable<type_of_object>,  just hover over your 'var' to see what it is.  I find this very useful as you can funnel your methods down to one cetnralized area, preventing copy/paste syndrome and centralizing your code.

// this takes in an entityset and 
public static IEnumerable<someObject> SomeMethod(IEnumerable<someObject> obs)
{
  // now run a query on your 'obs' object
  return from x in obs where something == somethingElse select x;
}

                                              
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by: yami_riderPosted on 2009-10-01 at 06:58:44ID: 31633835

Thank you, daryal was right and in fact that is what I am doing I have a business layer talking to a data access layer all of the actual data and connection handling is occuring at the lowest layer.  

Taking naspinski's suggestion in the business layer I have methods such as getcustomers, which inside is performing a LINQ query.

Thank you again.

20120131-EE-VQP-002

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