[ Team LiB ] Recipe Selecting the Top n Rows in a DataTable Problem You want to create a grid that shows the t op five rows in a DataTable, based on the values in one of the columns. Solution Use an appropriate sort order with a DataView filter. | Team LiB Recipe Selecting the Top n Rows in a DataTable Problem You want to create a grid that shows the t op five rows in a DataTable based on the values in one of the columns. Solution Use an appropriate sort order with a DataView filter. The sample code contains two event handlers Sets up the sample by creating a DataTable containing the Orders table from the Northwind sample database. The default view of the table is bound to the data grid on the form. Select Builds a filter on the DataView to limit the number of rows to the user-specified count with the largest Freight values. The C code is shown in Example 3-10. Example 3-10. File Namespaces variables and constants using System using using using using using private DataView dv Table name constants private const String ORDERS_TABLE Orders Field name constants private const String ORDERID_FIELD OrderlD private const String FREIGHT_FIELD Freight . . . private void DataViewTopNSelectForm_Load object sender e Fill the Orders table. SqlDataAdapter da new SqlDataAdapter SELECT FROM Orders S ql_ConnectString DataTable dt new DataTable ORDERS_TABLE dt dt Get the default view for the table and bind it to the grid. dv dv private void selectButton_Click object sender e This example will select the top n freight values. Set the field name variable. String topNFieldName FREIGHT_FIELD int topN 0 try topN if topN 0 Enter an Integer greater than 0. return catch Enter an Integer greater than 0. return Clear the filter on the view. Sort the view descending on the top
