is it possible to add DataRelation to DataSet if child table contains rows that have no parent in pa
- by matti
If I fill the DataSet with DataAdapters that select all rows from Orders and Customers and call:
private void CreateRelation()
{
// Get the DataColumn objects from two DataTable objects
// in a DataSet. Code to get the DataSet not shown here.
DataColumn parentColumn =
DataSet1.Tables["Customers"].Columns["CustID"];
DataColumn childColumn =
DataSet1.Tables["Orders"].Columns["CustID"];
// Create DataRelation.
DataRelation relCustOrder;
relCustOrder = new DataRelation("CustomersOrders",
parentColumn, childColumn);
// Add the relation to the DataSet.
DataSet1.Relations.Add(relCustOrder);
}
(from http://msdn.microsoft.com/en-us/library/system.data.datarelation.aspx)
there will be a runtime error if there is orders that do not have customers. This might happen when a buggy program has not deleted customer's orders when customer was deleted.
What can I do except put Orders select string a additional where-condition:
CUSTID IN (SELECT DISTINCT CUSTID FROM CUSTOMERS)
OR: is it really that way (that all children have to have parents)? My code might have a bug also. The exception occurs when IN MY CODE I add the relation to filled DataSet. The exception is:
An unhandled exception of type 'System.ArgumentException' occurred in System.Data.dll
Additional information: This constraint cannot be enabled as not all values have corresponding parent values.
Thanks & Best Regards - Matti
