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C#

Posted by Cameron Byfield
Cameron Byfield
151 Points

Link ID in one list to an ID in another

Hi, I am creating a program which contains two lists - one which is _categories and one which is _items.

Both of the lists have category ID's and the items which are associated with the particular category have matching category ID's.

I need to link them together and I'm using MS Visual Basic to do this but can't get it to work. Here is an example of my coding.

Private _categories As List(Of Categories)

Private _items As List(Of Items)

Public Sub New()

// I have set the properties of the list to be category ID and category name _categories = New List(Of Categories) _categories.Add(New Categories(1, "Items on Wheels")) ' items A0001 to A0005

//I have set the properties of the items list to be int ItemID, string Itemcode, string CategoryID, string Itemdescription and bool onorder _items = New List(Of Items) _items.Add(New Items(1, "A0001", 1, "Horse on Wheels", 5, False)) _items.Add(New Items(2, "A0002", 1, "Elephant on Wheels", 5, False)) _items.Add(New Items(3, "A0003", 1, "Dog on Wheels", 5, False))

//As you can see, all of the ItemIDs above match to the categoryID of Items on Wheels. here is the code that I have written to attempt to get them to match up but it is not working

Public Function Getitems(categoryID As Integer) As IList(Of Categories) Dim result = From i In _items Where i.CategoryID = categoryID Select i Return result.ToList

It would be great if I could get some help!

2 Answers

Chris Jones
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Chris Jones
Java Web Development Techdegree Graduate 23,933 Points
Chris Jones
.a{fill-rule:evenodd;}techdegree seal-36
Chris Jones
Java Web Development Techdegree Graduate 23,933 Points

Hey Cameron, if I understand you correctly, you're trying to create a new list that contains all items that have a category, right?

Could you do something like:

public List<Items> getItems(int categoryID, List<Items> _items)
{
  List<Items> categoryItems = new List<Items>();
  foreach (Items item in _items)
  {
      if (item.CategoryID == categoryID) 
      {
        categoryItems.Add(item);
      }
  }
  return categoryItems;
}

Also, are you pulling these two lists from a database? If so, you can probably have the database join the Category and Item entities together so the record set will be returned to your application with the entities already joined.

Let me know if I misunderstood something or you have any more questions :)!

James Churchill
STAFF
James Churchill
Treehouse Teacher
James Churchill
James Churchill
Treehouse Teacher

Cameron,

You don't show the code where you call the Getitems function. Seeing that function call would be helpful.

Also, try setting a breakpoint in the Getitems function and debug your app. When you hit your breakpoint you can then verify the value of the categoryID parameter, which is where I'd start with debugging your problem.

Thanks ~James