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Retrieving Parent and Child DataTable records

Posted by Mukesh Kumar Blogs | ADO.NET Jun 24, 2011
It’s easy to retrieve data that capitalizes on relationship after establishing a parent-child relationship between two tables in a DataSet

Retrieving Parent and Child DataTable records

It's easy to retrieve data that capitalizes on relationship after establishing a parent-child relationship between two tables in a DataSet. The DataRow class includes two methods— GetChildRows and GetParentRow—that retrieve the relevant row(s) at the other end of a linked relationship. Because a column could be involved in multiple relationships, you must pass either the name or the instance of the relationship to the relevant method.

 

 Following code sample shows working of GetParentRow method

            DataTable objDtOrder = DataSet1.Tables["Order"];

            DataRelation objRelation = objDtOrder.ParentRelations[0];

            DataRow parentRow;

            foreach (DataRow row in objDtOrder.Rows)

            {

                parentRow = row.GetParentRow(objRelation);

                Console.Write("\child row: " + row[1]);

                Console.Write("\parent row: " + parentRow[1] + "\n");

            }

 

 

Following code sample shows working of GetChildRows method

 DataRow[] arrRows;

            foreach (DataRelation myRelation in myTable.ChildRelations)

            {

                foreach (DataRow myRow in myTable.Rows)

                {

                    arrRows = myRow.GetChildRows(myRelation);

                    // Print values of rows.

                    for (int i = 0; i < arrRows.Length; i++)

                    {

                        foreach (DataColumn myColumn in myTable.Columns)

                        {

                            Console.WriteLine(arrRows[i][myColumn]);

                        }

                    }

                }

            }

 

The DataRow class also includes a method named GetParentRows that returns multiple parent rows for a single child record. This is useful for parent-child relationships that are linked on columns other than the parent's primary key.

 Following code sample shows working of GetParentRows method

 

            DataRelation relation = null;

            DataRow[] arrRows = null;

            DataRow row = null;

            int i = 0;

            DataColumn column = null;

 

            foreach (DataRelation objRelation in objTable.ParentRelations)

            {

                relation = objRelation;

                foreach (DataRow objRow in objTable.Rows)

                {

                    row = objRow;

                    arrRows = row.GetParentRows(relation);

                    // Print values of rows.

                    for (i = 0; i <= arrRows.GetUpperBound(0); i++)

                    {

                        foreach (DataColumn objColumn in objTable.Columns)

                        {

                            column = objColumn;

                            Console.WriteLine(arrRows[i][column.ColumnName]);

                        }

                    }

                }

            }

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