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extracting fields from my lambda expression

Posted on 2012-03-29
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Last Modified: 2012-03-29
I have the following line of code in a function in my unit of work:
Customer c = Customers.FindWhere(x => x.Username == username).FirstOrDefault();

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The function that this code is in however simply wants to return the "ID" field of the customer.

Instead of asking for all the customer fields, is there a way of just saying give me the id field?

The generic function .findwhere is using e.f 4.1
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Question by:scm0sml
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6 Comments
 
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Expert Comment

by:käµfm³d 👽
ID: 37784432
If I'm understanding the issue correctly, then I think you can use:

var c = Customers.FindWhere(x => x.Username == username).Select(x => x.ID).FirstOrDefault();

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Author Comment

by:scm0sml
ID: 37784446
I was thinking that but I get cannot implicitly convert type int to customer...?
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Accepted Solution

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käµfm³d   👽 earned 2000 total points
ID: 37784498
Yes, I had to change "Customer c" to "var c" because I wasn't sure what the type of "ID" was. You say that the function "wants to return the 'ID' field of the customer", so I expected that you have specified your function's return value to match the type of "ID"--which in this case seems to be int. The var I used should take care of any typing issues, but you can replace it with int if it makes you more comfortable.
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Author Comment

by:scm0sml
ID: 37784508
ah right i think where i was getting confused was i though the select was just saying populate the id field of the returned customer object as opposed to just returning an int.

That works for me in this case.

If I did want to return say 3 of the 10 fields, could I do that using the lambda?
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LVL 75

Expert Comment

by:käµfm³d 👽
ID: 37784524
Sure:

var c = Customers.FindWhere(x => x.Username == username)
                 .Select(x => new Customer()
                              {
                                  ID = x.ID,
                                  FName = x.FName,
                                  LName = x.LName,
                              })
                 .FirstOrDefault();

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Author Comment

by:scm0sml
ID: 37784629
ah ha...

good man.
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