Add one list to another in C#

Question

I'm trying to add one list to another . So I have this main list that I'm going to build. I loop through records and built a list and want this list to main list every time I loop. I'm trying to do this in C#. I'm using following code. Add() function is not working.I'm getting syntax error.

 IList<CgValDetail> cgValDetail = null;
            //Get cgValDetails for each control
            foreach (UiControlScreenMetaData tempUiControls in uiControls)
            {
                if (tempUiControls.CgValId == null)
                {
                    continue;
                }
                IList<CgValDetail> tempCgValDetail = Retrieval<CgValDetail>.Search(new { CgValId = tempUiControls.CgValId }).ToList();
                if (!tempCgValDetail.Any())
                {
                    _foundationService.LogBusinessError(null, new ParameterBuilder("CgValId", tempUiControls.CgValId), "Invalid_CgValId_found");
                    return false;
                }
                //Add tempCgValDetail List to main list which is cgValDetail
                cgValDetail.Add(tempCgValDetail);


            }

Are you searching for AddRange? `cgValDetail.AddRange(tempCgValDetail);` — Blas Soriano, Jun 05 '15 at 03:10
I tried using that but I'm getting build error saying: cgValDetail doesn't contain definition for AddRange() — Jaspreet Deol, Jun 05 '15 at 03:15
Didn't noticed its an IList. You cannot use AddRange on IList. Why are you using IList instead of List? — Blas Soriano, Jun 05 '15 at 03:20
possible duplicate of [Joining two lists together](http://stackoverflow.com/questions/1528171/joining-two-lists-together) — Fragment, Jun 05 '15 at 04:00
@Fragment that would be true if you don't consider the use of IList (besides adding to null). — Blas Soriano, Jun 05 '15 at 04:03

score 1 · Answer 1 · edited May 23 '17 at 11:58

1

Take a look at AddRange.

var firstList = new List<string>();
var secondList = new List<string>() { "a", "b" };

firstList.AddRange(secondList);

You mentioned that you don't have access to AddRange... The problem is that you're using an IList, which doesn't implement AddRange. Check this out for more on why: Why doesn't IList support AddRange

I would advise you to switch to List.

edited May 23 '17 at 11:58

Community

1
1

answered Jun 05 '15 at 03:16

Brian MacKay

31,133
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anhtv13 · Answer 2 · 2015-06-05T03:32:05.237

0

Your cgValDetail is null. That's why when you add(...), you get syntax error.

Create a new IList<CgValDetail>

IList<CgValDetail> cgValDetail = new List<CgValDetail>();

Why didn't you use List<T> in stead of IList<T>?

edited Jun 05 '15 at 03:32

answered Jun 05 '15 at 03:18

anhtv13

1,636
4
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1

How will you create an instance of `interface`? – Hari Prasad Jun 05 '15 at 03:26

score 0 · Answer 3 · edited May 23 '17 at 11:58

0

You forgot to new it.

Just a simple example:

List<a> aList= new List<a>();
List<aList> List_aList = new List<aList>();
List_aList.add(new aList());

Here the link to same question.

edited May 23 '17 at 11:58

Community

1
1

answered Jun 05 '15 at 03:29

Robert Ling

33
1
8

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in your code you are trying to create an instance for an interface, code will not compile. – Hari Prasad Jun 05 '15 at 03:38

score 0 · Answer 4 · answered Jun 05 '15 at 03:31

First, you need to instantiate cgValDetail as a new list, not a null.

Then you should decide if you want to declare cgValDetail as IList instead of a List. If yes, try this:

IList<CgValDetail> cgValDetail = new List<CgValDetail>();
//Get cgValDetails for each control
foreach (UiControlScreenMetaData tempUiControls in uiControls)
{
    if (tempUiControls.CgValId == null)
    {
        continue;
    }
    IList<CgValDetail> tempCgValDetail = Retrieval<CgValDetail>.Search(new { CgValId = tempUiControls.CgValId }).ToList();
    if (!tempCgValDetail.Any())
    {
        _foundationService.LogBusinessError(null, new ParameterBuilder("CgValId", tempUiControls.CgValId), "Invalid_CgValId_found");
        return false;
    }
    //Add tempCgValDetail List to main list which is cgValDetail
    ((List<CgValDetail>)cgValDetail).AddRange(tempCgValDetail);
}

But I wonder why just not using a List instead of IList.

List<CgValDetail> cgValDetail = new List<CgValDetail>();
//Get cgValDetails for each control
foreach (UiControlScreenMetaData tempUiControls in uiControls)
{
    if (tempUiControls.CgValId == null)
    {
        continue;
    }
    List<CgValDetail> tempCgValDetail = Retrieval<CgValDetail>.Search(new { CgValId = tempUiControls.CgValId }).ToList();
    if (!tempCgValDetail.Any())
    {
        _foundationService.LogBusinessError(null, new ParameterBuilder("CgValId", tempUiControls.CgValId), "Invalid_CgValId_found");
        return false;
    }
    //Add tempCgValDetail List to main list which is cgValDetail
    cgValDetail.AddRange(tempCgValDetail);
}

score 0 · Answer 5 · answered Jun 05 '15 at 06:39

0

Maybe, you can use "UNION" in Linq (if you don't really care about performance or result set is not big enough).

cgValDetail.Add(tempCgValDetail);

change to

cgValDetail = cgValDetail.Union(tempCgValDetail.Select(a => a)).ToList();

answered Jun 05 '15 at 06:39

Heinz Siahaan

355
2
10

Add one list to another in C#

5 Answers5