DataRelation question

[OL922]

I'm using two dataadapters to bring in 2 tables into a dataset and then creating a one to many relationship but I keep on getting this error

 

"Object Reference not set to an instance of the object"

 

Here's the code

 

can someone help

Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Documents and Settings\Administrator\My Documents\Access Database\SimpleDataAccessExample.mdb;" 
           'Connection object
           Dim mdbConn As OleDbConnection = New OleDbConnection(strConn)

           'DataAdapter for the customer table
           Dim daCustomer As OleDbDataAdapter = New OleDbDataAdapter("SELECT * FROM Customer", mdbConn) 'where City=" & txtSearch.Text, mdbConn)

           ' DataAdapter for the orders table
           Dim daOrders As OleDbDataAdapter = New OleDbDataAdapter("SELECT * FROM Orders", mdbConn)

           '----------------------------------------------------------
           'opening and closing
           mdbConn.Open()

           'Create DataSet
           Dim dsCustomerOrder As New DataSet()

           'Fill DataSet
           daCustomer.Fill(dsCustomerOrder)
           daOrders.Fill(dsCustomerOrder)

           'Close the connection
           mdbConn.Close()
           '----------------------------------------------------------

           'The tables are now loaded into the dataset and the 
           'relationship between the Customer and Orders table can be added
           Dim CustOrderRel As DataRelation = dsCustomerOrder.Relations.Add("CustOrder", _
           dsCustomerOrder.Tables("Customer").Columns("CustomerID"), _
           dsCustomerOrder.Tables("Orders").Columns("CustomerID"))

           Dim pRow, cRow As DataRow

           For Each pRow In dsCustomerOrder.Tables("Customer").Rows
               Console.WriteLine(pRow("CustomerID").ToString())
           Next

           For Each cRow In pRow.GetChildRows(CustOrderRel)
               Console.WriteLine(vbTab & cRow("OrderId").ToString())
           Next

       Catch ex As Exception
           MsgBox(ex.Message & " ErrorSource: " & ex.Source & "  Stacktrace: " & ex.StackTrace)
       End Try

[OL922]

The problem seems to be that the instance of the DataRelation object is not getting created.......?

[Nerseus]

Are you getting the error on the line that sets up CustOrderRel, your DataRelation? You seem to be doing it correctly so maybe the table and/or column name is wrong? It shouldn't be case sensitive, but maybe the spelling is off...

 

-nerseus

[OL922]

My mistake had to do with the fill method. If I don't use the overloaded version that takes in the name of the table that I specify as the second argument, then a table with the name "Table" is created when I use the fill method with just the dataset as the parameter. So i was referring to the wrong tables names when I was trying to instantiate the datarelation object.

 

So this works fine

daCustomer.Fill(dsCustomerOrder, "Customer")
daOrders.Fill(dsCustomerOrder, "Order")