tailieunhanh - Counting Records in a DataReader

[ Team LiB ] Recipe Counting Records in a DataReader Problem You want to determine how many records there are in a DataReader. Solution Use one of the following three techniques | Team LiB Recipe Counting Records in a DataReader Problem You want to determine how many records there are in a DataReader. Solution Use one of the following three techniques Iterate over the rows in the DataReader. Issue a COUNT query as part of a batch query. Note that not all data sources support batch queries. If not execute the statements separately one after the other for a similar result. Use the @@ROWCOUNT function to return the number or rows in a DataReader after the DataReader has been closed. This technique is SQL Server specific. The sample code uses a single stored procedure SP0207_GetOrders Returns a result set containing all records in the Orders table in Northwind. Also the stored procedure returns the @@ROWCOUNT value for the query in an output parameter. The stored procedure is shown in Example 2-7. Example 2-7. Stored procedure SP0207_GetOrders ALTER PROCEDURE SP0207_GetOrders @RowCount int output AS set nocount on select from Orders set @RowCount @@ROWCOUNT RETURN The C code is shown in Example 2-8. Example 2-8. File Namespaces variables and constants using System using using using . . . Batch query to retrieve the COUNT of records and all of the records in the Orders table as two result sets. String sqlText SELECT COUNT FROM Orders SELECT FROM Orders Create the connection. SqlConnection conn new SqlConnection Sql_ConnectString SqlCommand cmd new SqlCommand sqlText conn Create a DataReader on the first result set. SqlDataReader dr Get the count of records from the select count statement. Orders table record count using COUNT 0 Move to the data result set. int count 0 Iterate over the records in the DataReader. while count . . . Do something interesting with the data here. Close the DataReader and the connection.