Linking Data Tables Programmatically

I have two tables (in memory only), which belong to a dataset. The expense table is bound to a DataGridView. How can I link the two tables so that instead of showing the CategoryID in the grid, it shows the actual CategoryName associated with the CategoryID on the Expense table?

' Category Table
dtCategory = New DataTable("Category")
dtCategory.Columns.Add("CategoryID", GetType(Integer))
dtCategory.Columns.Add("CategoryName", GetType(String))
dtCategory.Columns.Add("Description", GetType(String))

' Expense Table
dtExpense = New DataTable("Expense")
dtExpense.Columns.Add("ExpenseID", GetType(Integer))
dtExpense.Columns.Add("CategoryID", GetType(String))
dtExpense.Columns.Add("Amount", GetType(Integer))

' Dataset
dsBudget = New DataSet("Budget")
dsBudget.Tables.Add(dtCategory)
dsBudget.Tables.Add(dtExpense)

' DataGridView
grdSelection.AutoGenerateColumns = False
grdSelection.DataSource = dsBudget
grdSelection.DataMember = "Expense"
jmsbtylerAsked:
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Bob LearnedCommented:
Yeah, I couldn't see declarations, but I noticed the DataGridView comment, and I didn't want to make any assumptions.

Here is an example of adding a column programmatically:

        Me.DataGridView1.AutoGenerateColumns = False
        Me.DataGridView1.Columns.Clear()

        Dim column As New DataGridViewTextBoxColumn
        column.DataPropertyName = "name"
        column.HeaderText = "Name"
        column.AutoSizeMode = DataGridViewAutoSizeColumnMode.AllCells

        Me.DataGridView1.Columns.Add(column)

Bob
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Bob LearnedCommented:
Add a DataRelation:

      ' Category Table
        dtCategory = New DataTable("Category")
        dtCategory.Columns.Add("CategoryID", GetType(Integer))
        dtCategory.Columns.Add("CategoryName", GetType(String))
        dtCategory.Columns.Add("Description", GetType(String))

        ' Expense Table
        dtExpense = New DataTable("Expense")
        dtExpense.Columns.Add("ExpenseID", GetType(Integer))
        dtExpense.Columns.Add("CategoryID", GetType(String))
        dtExpense.Columns.Add("Amount", GetType(Integer))

        ' Dataset
        dsBudget = New DataSet("Budget")
        dsBudget.Tables.Add(dtCategory)
        dsBudget.Tables.Add(dtExpense)

        ' Relation
        dsBudget.Relations.Add("Category_Expense", New DataColumn() {dtCategory.Columns("CategoryID")}, New DataColumn() {dtExpense.Columns("CategoryID")})

        ' DataGridView
        grdSelection.AutoGenerateColumns = False
        grdSelection.DataSource = dsBudget
        grdSelection.DataMember = "Expense"

Bob
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jmsbtylerAuthor Commented:
Thanks for your response.

I've since looked into the Data Relation, and played around with some things but I am still not sure what to do to get it to work in the grid.

What do I need to set the DataProperty Name to for the CategoryID column? (The grid is linked to the Expense Table)

Bruce
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Bob LearnedCommented:
The DataGrid can display parent/child records with a plus sign to expand, but it's a little weird, and a lot of people don't like that.  You need to bind columns in the DataGrid to the text columns, and not the primary key columns.

Bob
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jmsbtylerAuthor Commented:
How do I bind the columns in the grid to Text columns instead of the fields from the table?

Instead of binding the table to the grid, do I need to loop through the table and manually insert each row into the grid (while looking up the Category Name using the ID)?
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Bob LearnedCommented:
What .NET version are you using?  2002, 2003, or 2005?

Bob
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jmsbtylerAuthor Commented:
2005

Sorry, I should have put that in my original question.

Bruce
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jmsbtylerAuthor Commented:
It works!

I left the datagrid bound to the "Expense" table, and then I created a new column called "CategoryName". I then added the following logic to loop through each row in the datagrid and populate the Categoryname column based on the CategoryID.

For Each Row As DataGridViewRow In grdSelection.Rows
       Dim CategoryID As Integer = Row.Cells("CategoryID").Value
       Dim FoundRow As DataRow = dsBudget.Tables("Category").Rows.Find(CategoryID)
       If FoundRow IsNot Nothing Then
                Row.Cells("CategoryName").Value = FoundRow(1).ToString
       End If
Next

Thanks for all of your help Bob! I really appreciate it!
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