3.4. Navigating Between Parent and Child Records Using a DataRelation
Problem
You want to navigate between
the parent and child records in a
hierarchical DataSet
.
Solution
Use a DataRelation
to find the child rows for a
parent row in a related table, or to find the parent row for a child
row in a related table.
The sample code starts by creating a DataSet
containing the Orders and Order Details tables from the Northwind
sample database and a relation between them. The code then iterates
over the Orders and uses the relation to return all Order Detail rows
for each order. Finally, the sample code retrieves the CustomerID
field from the parent row and displays it for each child.
The C# code is shown in Example 3-4.
Example 3-4. File: NavigateDataRelationForm.cs
// Namespaces, variables, and constants using System; using System.Configuration; using System.Text; using System.Data; using System.Data.SqlClient; // Table name constants private const String ORDERS_TABLE = "Orders"; private const String ORDERDETAILS_TABLE = "OrderDetails"; // Relation name constants private const String ORDERS_ORDERDETAILS_RELATION = "Orders_OrderDetails_Relation"; // Field name constants private const String ORDERID_FIELD = "OrderID"; private const String PRODUCTID_FIELD = "ProductID"; private const String QUANTITY_FIELD = "Quantity"; private const String CUSTOMERID_FIELD = "CustomerID"; // . . . DataSet ds = new DataSet( ); SqlDataAdapter da; // Fill the Order table and add it to the DataSet. da = new SqlDataAdapter("SELECT ...
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