Navigating Hierarchical Data

The strongly typed DataSet provides two methods for each DataRelation , TableName Row( ) and TableName Rows( ), to facilitate navigating records in parent child relationships. These methods are similar to the GetParentRow( ) and GetChildRows( ) methods in the untyped DataSet. The TableName Row( ) method is defined for the child table and retrieves the parent row for a DataRow. The TableName Rows( ) method is defined for the parent table in a relationship and retrieves the child rows for a DataRow.

The strongly typed DataSet methods encapsulate the DataRelations defined within the DataSet so a reference to the DataRelation or the name of the DataRelation isn’t required when navigating the hierarchy of records. The following sample demonstrates using the strongly typed DataSet methods to navigate a hierarchy of records:

// strongly typed DataSet called Northwind containing Orders table and 

// OrderDetails table, related through the OrderID field

Northwind ds = new Northwind();



// ... code to fill the Orders and Order Details tables in the DataSet



foreach(Northwind.OrdersRow ordersRow in ds.Orders)

{

    // iterate the collection of order details for the order through

    // the GetOrderDetailsRow accessor

    foreach(Northwind.Order_DetailsRow orderDetailsRow in

        ordersRow.GetOrder_DetailsRows())

    {

        // get the CustomerID from the parent row, through the

        // OrdersRow property of the child row

        String customerId = orderDetailsRow.OrdersRow.CustomerID;

        

        // get the ProductID

        Int32 productId = orderDetailsRow.ProductID;

    }

}

This example shows comparable code using an untyped DataSet:

// untyped DataSet containing Orders table and 

// OrderDetails table, related through the OrderID field

DataSet ds = new DataSet();



// ... code to define or retrieve the schema for the Orders and

// [Order Details] tables schemas including creating DataRelation objects

// ... code to add new rows to the Orders and [Order Details] tables



foreach(DataRow ordersRow in ds.Tables["Orders"].Rows)

{

    foreach(DataRow orderDetailsRow in

        ordersRow.GetChildRows("Order_OrderDetails"))

    {

        // get the CustomerID from the parent row

        String customerId  = 

             orderDetailsRow.GetParentRow("Order_OrderDetails")

            ["CustomerID"].ToString();

        

        // get the ProductID

        Int32 productId = (Int32)orderDetailsRow["ProductID"];        

    }

}