?
Solved

join linq to sql with an array

Posted on 2011-02-25
8
Medium Priority
?
732 Views
Last Modified: 2013-11-11
Ok just getting started with Linq and I've stumbled on an issue.

I've got a Linq query that is coming from a SQL DB that I have read only access to.

 
RapCourseRosters rd = new RapCourseRosters();
            var query =
                from classes in rd.Events_and_Classes 
                join courses in rd.Courses on classes.Course_ID equals courses.Course_ID
                where classes.End_Date.CompareTo(startyyyymmdd) >= 0
                && classes.End_Date.CompareTo(endyyyymmdd) <= 0
                && courses.Course_Type == "ACC"
                orderby classes.End_Date.ToString()
              select new { 
                  End_Date = classes.End_Date,
                  End_Date_Norm = classes.End_Date.Substring(4,2) + "/" + classes.End_Date.Substring(6,classes.End_Date.Length) + "/" + classes.End_Date.Substring(0,4),
                  Start_Date = classes.Start_Date, 
                  Event_Name = classes.Event_Name, 
                  Event_ID = classes.Event_ID,
                  Course_ID = courses.Course_ID
              };

Open in new window


I want to join this data to data on EventID to data  that I have in a separate .Csv file lets say:

csvEventID            |       csvLastAccessed
--------------------------------------------------------
CE-1212-880         |       2/24/2011
CE-1212-881         |       2/21/2011
CE-1212-887         |       2/24/2009
CE-1212-771         |       7/02/2010

I can do this via temporary recordsets but as a learning exercise I'm trying to do it in pure Linq. Is there an elegant way to join them using Linq?

Thanks

Michael




0
Comment
Question by:mcunn
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
  • 3
8 Comments
 
LVL 75

Expert Comment

by:käµfm³d 👽
ID: 34982373
Hmmm...   Interesting. Should be a simple enough task, though  = )

Let's try this (Note: there is no error checking):
var joined = from line in System.IO.File.ReadAllLines("C:\\path\\to\\file.txt")
             let parts = line.Split(new char[] { ',' })[0]
             join rcr in rd
             on rcr.Event_ID equals parts[0]
             select new { End_Date = rcr.End_Date,
                          End_Date_Norm = rcr.End_Date_Norm,
                          Start_Date = rcr.Start_Date,
                          Event_Name = rcr.Event_Name,
                          Event_ID = rcr.Event_ID,
                          Course_ID = rcr.Course_ID,
                          Last_Accessed = parts[1]
             };

Open in new window

0
 

Author Comment

by:mcunn
ID: 34982731
Kaufmed,

Thanks for the code I'm trying to understand what you are doing in this block

 
join rcr in rd
on rcr.Event_ID equals parts[0]

Open in new window


Im getting an error on the join "RCR is not in scope on left side of  join"

Thanks

Michael

0
 
LVL 63

Assisted Solution

by:Fernando Soto
Fernando Soto earned 800 total points
ID: 34982870
Hi mcunn;

Modifying Kaufmed solution, try it like this.

Fernando
var joined = from line in System.IO.File.ReadAllLines("C:\\path\\to\\file.txt")
             let parts = line.Split(new char[] { ',' })[0]
             join rcr in query
             on parts[0] equals rcr.Event_ID 
             select new { End_Date = rcr.End_Date,
                          End_Date_Norm = rcr.End_Date_Norm,
                          Start_Date = rcr.Start_Date,
                          Event_Name = rcr.Event_Name,
                          Event_ID = rcr.Event_ID,
                          Course_ID = rcr.Course_ID,
                          Last_Accessed = parts[1]
             };

Open in new window

0
Cloud Training Guides

FREE GUIDES: In-depth and hand-crafted Linux, AWS, OpenStack, DevOps, Azure, and Cloud training guides created by Linux Academy instructors and the community.

 
LVL 75

Accepted Solution

by:
käµfm³d   👽 earned 1200 total points
ID: 34982925
Thx FernandoSoto! I admit the code was untested  = )


As far as the intent: I took your requirement literally and read each line of the file into an (implicit) array. At that point, however, the text is still just a string, so it has to be split on the comma (since you said CSV). I'm holding the split in a temporary local (to the Linq query) variable called "parts". Given your description above, the first index of parts should be the "csvEventID"; the second index should be the "csvLastAccessed". The query is joining the Event_ID from "rd" to the "csvEventID" of the array (index 0).
0
 

Author Closing Comment

by:mcunn
ID: 34983169
Thanks guys that's exactly what I was looking for.
0
 
LVL 75

Expert Comment

by:käµfm³d 👽
ID: 34983190
NP. Glad to help  : )
0
 
LVL 75

Expert Comment

by:käµfm³d 👽
ID: 34983248
Hmmm....  you've probably already accounted for this, but I can't see why I originally included the [0] at the end of the split. That, from what I can see, would set parts to the value of the first index of the array. Unless I'm missing something, remove the [0] from the end of the "let" line  : )
0
 

Author Comment

by:mcunn
ID: 34997136
Yep, I caught it... totally forgot to post the correction as I was so excited it actually worked.

Thanks again!

0

Featured Post

Docker-Compose to Simplify Multi-Container Builds

Our veteran DevOps Author takes you through how to build a multi-container environment, managed with a single utility in order to simplify your deployments.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Entity Framework is a powerful tool to help you interact with the DataBase but still doesn't help much when we have a Stored Procedure that returns more than one resultset. The solution takes some of out-of-the-box thinking; read on!
Performance in games development is paramount: every microsecond counts to be able to do everything in less than 33ms (aiming at 16ms). C# foreach statement is one of the worst performance killers, and here I explain why.
NetCrunch network monitor is a highly extensive platform for network monitoring and alert generation. In this video you'll see a live demo of NetCrunch with most notable features explained in a walk-through manner. You'll also get to know the philos…
In this video, Percona Director of Solution Engineering Jon Tobin discusses the function and features of Percona Server for MongoDB. How Percona can help Percona can help you determine if Percona Server for MongoDB is the right solution for …
Suggested Courses

765 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question