[新手點滴] IDbCommand.Prepare()方法。

今天在逛新聞群組的時候無意中看到了SqlCommand.Prepare()方法。在IDbCommand介面上就定義了Prepare()方法，這個方法可以把CommandType為Text的SQL語句提前在資料庫中編譯為一個臨時的StoredProcedure然後再執行，這樣對於需要多次執行的DbCommand來說，可以提高一定的執行效率：）注意：請在指定了Command的Connection之後再調用Prepare()方法。

此方法在msdn上的介紹如下：

Creates a prepared (or compiled) version of the command on the data source.
Remarks

If the CommandType property is set to TableDirect, Prepare does nothing. If CommandType is set to StoredProcedure, the call to Prepare should succeed, although it may result in a no-op.

Example
The following example creates an instance of the derived class, OleDbCommand, and opens the connection. The example then prepares a stored procedure on the data source by passing a string that is a SQL Select statement and a string to use to connect to the data source.
[C#]

public void OleDbCommandPrepareEx() {
   int  id = 20;
   string  desc = "myFirstRegion" ;
   OleDbConnection rConn = new OleDbConnection("Provider=SQLOLEDB;Data Source=localhost;Integrated Security=SSPI;Initial Catalog=Northwind;");
   rConn.Open();
   OleDbCommand command    = new OleDbCommand(null, rConn);

   // Create and prepare an SQL statement.
   command.CommandText = "insert into Region (RegionID, RegionDescription) values (@id, @desc)" ;
   command.Parameters.Add ( "@id", id) ;
   command.Parameters.Add ( "@desc", desc) ;
   command.Prepare() ;  // Calling Prepare after having set the Commandtext and parameters.
   command.ExecuteNonQuery();

   // Change parameter values and call ExecuteNonQuery.
   command.Parameters[0].Value = 21;
   command.Parameters[1].Value = "mySecondRegion";
   command.ExecuteNonQuery();
}