Concat() is not working in C#

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I have created an object of type List and I am concatinating another collection of type IEnumerable into it but the the object always showed zero record while debugging.

When I debugged, the Count for obj was zero

obj = 0

Where have I gone wrong? Or is there another way to do it? I even tried Add(), but it didn't work

What I have tried:

public IEnumerable<Dealer> GetDealerData(param)
{
    var obj = new List<Dealer>();

    foreach(var item in param)
    {
        var ob = ObjectFactory.GetInstance<IDealerRepository>().MyFunc(item.Id);
        //ob is of type IEnumerable<Dealer>

        obj.Concat(ob);
    }

    return obj;
}

Posted 19-Feb-19 2:12am

Member 13974276

Updated 19-Feb-19 3:10am

v2

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2 solutions

Solution 1

Assuming you can get that to compile - it won't as shown - start with the debugger: put a breakpoint on the line

var obj = new List<Dealer>();

and look at the content of param to find out how many objects it contains.

At a guess, none. No objects, no foreach body execution, no objects added to the collection. But you can only confirm that with your code running with your data - so you need the debugger to confirm, and then use the stack trace to find out why. But even then, Concat does not modify the original collection, so you'd need to save the result to get anywhere.

Sorry, but we can't do that for you!

Posted 19-Feb-19 2:30am

OriginalGriff

Updated 19-Feb-19 2:32am

v3

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Member 13974276 · Accepted Answer · 2019-02-19T03:11:00

Solution 2

Everything was fine. I had to use AddRange() instead of Concat()

obj.AddRange(ob);

Posted 19-Feb-19 3:11am

Member 13974276

Comments

Richard Deeming 20-Feb-19 9:15am

Indeed - Concat[^] is an extension method which returns the concatenated sequence. It doesn't modify the input sequence in any way.