LINQ query to get result

Question

I have Student list with below data

/*----------------------- |Student | ------------------------- | ID | Name | Dept | ------------------------- | 101 | Peter | IT | | 102 | John | IT | | 103 | Ronald | Mech | | 104 | Sam | Comp | -----------------------*/

Other list say Extra with below data

/*---------------------- | StudentId | Dept | ------------------------ | 101 | Civil | | 103 | Chemical | ----------------------*/

Now I want following result

/*------------------------- |Student | --------------------------- | ID | Name | Dept | --------------------------- | 101 | Peter | Civil | | 102 | John | IT | | 103 | Ronald | Chemical | | 104 | Sam | Comp | -------------------------*/

Currently I have written below logic:

foreach(item in Extra) { //Search item in Student list //Update it }

I need more efficient way (don't want to use iteration) using LINQ.

anishMarokey · Accepted Answer · 2011-05-05 09:37:37Z

1

Try something like this. Didn't test it though.

var query = from s in student join e in extra on s.ID == e.StudentId select new {s.ID, s.Name, (e.Dept != null) ? e.Dept:s.Dept};

edited May 5, 2011 at 9:37

anishMarokey

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answered May 5, 2011 at 9:32

gordanvij

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2 Comments

meetjaydeep Over a year ago

I am using DataTable for Student. So when I write above query it will not update the row state. I need rowstate of the StudentIds 101 and 103 to be Modified.

Nappy Over a year ago

LINQ = Language Integrated Query: Queries by nature do not modify. You can interate over them, and do the stuff you need to do. If you want to get only the rows where the Depts differ, simply add where e.Dept != s.Dept.

Daniel Hilgarth · Accepted Answer · 2011-05-05 09:21:42Z

LINQ is using iteration internally, too, so there is no performance benefit in using LINQ. Because LINQ has very general implementations, it might even be slower, because it can't make assumptions about your data, which you can make in your custom loop.

Ok, agree with the performance issue. But can you give the LINQ query I just want to check how to use it in this case.

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