Ado. NET QuickStart-Returns a data value using the ExecuteScalar () method of the Command object

Related knowledge:

1. Some SQL operations, such as SUM, return only one data value from the database, not multiple rows of data
2. Although you can also use ExecuteReader () to return a DataReader object that represents that data value, it is more convenient to use the ExecuteScalar method of the Command object
3. ExecuteScalar () Method: The method can only execute SELECT statements and is typically used for statistics, such as returning the number of records that match a condition

code example:

1 usingSystem;2 usingSystem.Collections.Generic;3 usingSystem.Linq;4 usingSystem.Text;5 usingSystem.Threading.Tasks;6 usingSystem.Data;7 usingSystem.Data.SqlClient;8 9 namespaceConsoleApplication3Ten { One     class Program A     { -         Static voidMain (string[] args) -         { the             stringstrconn =@"Server=joe-pc;database=adventureworks_wroxssrs2012;uid=sa;pwd=root"; -SqlConnection conn =NewSqlConnection (strconn); -  -             stringStrcmd ="SELECT COUNT (*) from Production.productcategory"; +SqlCommand cmd =NewSqlCommand (STRCMD, conn); -  + Conn. Open (); A  at             intCount = Convert.ToInt32 (cmd. ExecuteScalar ());//ExecuteScalar Returns an object type -  -Console.WriteLine ("there are {0} rows of data. ", count); -  - Conn. Close (); -         } in     } -}

Ado. NET QuickStart-Returns a data value using the ExecuteScalar () method of the Command object