Issue with Primary Keys and child tables in dataset

[G_Waddell]

Hi,

I have an issue involving retrieving a set of child rows in a dataset.

I have populated a dataset with three tables Categories, Projects and Tasks. In the dataset relations I have set up a relationship between Categories and Projects and between Projects and Tasks.

Private Sub Defaults_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
....
with myDset
   .tables(0).TableName ="Categories"
   .tables(0).Columns("CategoryID").Unique = True
   .tables(1).TableName ="Projects"
   .tables(1).Columns("ProjectCode").Unique = True
   .tables(2).TableName ="Tasks"
   .tables(2).Columns("TaskCode").Unique = True
  with .relations
      .Add("ProjectCategory", myDSet.Tables("Categories").Columns("CategoryID"), myDSet.Tables("Projects").Columns("CategoryID"))
      .Add("ProjectTasks", myDSet.Tables("Projects").Columns("ProjectCode"), myDSet.Tables("Tasks").Columns("ProjectCode"))
  end with
end with
.....
end sub

This all works fine when I debug.

Using this dataset I wish to populate some comboboxes to allow the user to select a Category then a Project and get the list of
tasks in a listbox.

So I populate the category combo with no issue. However when I try and retrieve the selected row of the table I get an error stating that no primary key has been set.

Private Sub cbProjCat_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbProjCat.SelectedIndexChanged
....
dim Category as Dataitem 'custom class allows an id and string value to be passed into combobox

'Which Category has been selected
 Category = cbProjCat.SelectedItem
 'What is the ID?
 CategoryID = Category.ID
'Get this row in the Categories table in the Dataset 
 CategoryRow = myDSet.Tables("Categories").Rows.Find(CategoryID)
...
end sub

I tried setting the primarykey on the datatables like so but I get an error about it not accepting 1 dimensional arrays...

myDset.Tables("Categories").PrimaryKey = myDset.Tables("Categories").Columns("CategoryID")

Anyone out there have any ideas?
Do I need to set the Primarykey?
Does the primary key need to be composite i.e. two columns?
Thanks in advance

[kvprajapati]

Have a look,

Dim dt As New DataTable
        dt.Columns.Add("No", GetType(Integer))
        dt.Columns.Add("Name")

        dt.PrimaryKey = New DataColumn() {dt.Columns(0)}

[G_Waddell]

Have a look,

Dim dt As New DataTable
        dt.Columns.Add("No", GetType(Integer))
        dt.Columns.Add("Name")

        dt.PrimaryKey = New DataColumn() {dt.Columns(0)}

Thanks! thats did the job...