第三课 SqlCommand对象(翻译)_Sql Server_学习笔记★闵涛★计算机学习电脑编程软硬件技巧


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第三课 SqlCommand对象(翻译)

作者：闵涛文章来源：闵涛的学习笔记点击数：14795 更新时间：2007/11/14 13:12:47

            // prepare command string
             string deleteString = @"
                 delete from Categories
                 where CategoryName = ''''Other''''";

             // 1. Instantiate a new command
             SqlCommand cmd = new SqlCommand();

           // 2. Set the CommandText property
             cmd.CommandText = deleteString;

           // 3. Set the Connection property
             cmd.Connection = conn;

             // 4. Call ExecuteNonQuery to send command
             cmd.ExecuteNonQuery();
         }
         finally
         {
             // Close the connection
             if (conn != null)
           {
               conn.Close();
             }
         }
     }

     /// <summary>
     /// use ExecuteScalar method
     /// </summary>
     /// <returns>number of records</returns>
     public int GetNumberOfRecords()
     {
       int count = -1;

       try
       {
             // Open the connection
             conn.Open();

             // 1. Instantiate a new command
             SqlCommand cmd = new SqlCommand("select count(*) from Categories", conn);

             // 2. Call ExecuteNonQuery to send command
             count = (int)cmd.ExecuteScalar();
       }
         finally
         {
          // Close the connection
             if (conn != null)
             {
               conn.Close();
           }
       }
         return count;
     }
}

In Listing 1, the SqlConnection object is instantiated in the SqlCommandDemo structure. This is okay because the object itself will be cleaned up when the CLR garbage collector executes. What is important is that we close the connection when we are done using it. This program opens the connection in a try block and closes it in a finally block in each method.

在表1

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