asp.net 使用using代码块 摘

"ado.net 2.0 技术内幕

强烈建议在Using代码块内所有可能的位置创建短期生存对象。

Using 块确保及时在Using块内波发生未处理异常时, 也会在该代码块的末尾调用 Dispose 方法。

 

例子:

  
    

   
     string
   
      strConn, strSQL;
strconn 
   
     =
   
      
   
     @"
   
     Data Source=.\SQLExpress;
   
     "
   
      
   
     +
   
      
   
     "
   
     Initial Catalog = Northwind;Integrated Security=True;
   
     "
   
     ;
strSQL 
   
     =
   
      
   
     "
   
     SELECT CustomerID, CompanyName FROM Customers
   
     "
   
     ;
Using (SqlConnection cn 
   
     =
   
      
   
     new
   
      SqlConnection(strConn)) {
 Try {
 cn.Open();
 }
 Catch (SqlException ex) {
 Consolse.WriteLine(
   
     "
   
     Connect attempt failed
   
     "
   
     );
 Consolse.WriteLine(
   
     "
   
      {0}
   
     "
   
     , ex.Message);
 
   
     return
   
     ;
 }
 
 Using (SqlCommand cmd 
   
     =
   
      
   
     new
   
      SqlCommand(strSQL, cn) {
 
   
     try
   
      {
 
   
     using
   
      (SqlDataReader rdr 
   
     =
   
      cmd.ExecuteReader()) {
 
   
     while
   
      (rdr.Read())
 Console.WriteLine(rdr[ 
   
     "
   
     CompanyName
   
     "
   
     ]);
 rdr.Close();
 }
 }
 
   
     catch
   
      (SqlException ex) {
 Console.WriteLine(
   
     "
   
     Query failed
   
     "
   
     );
 Console.WriteLine(
   
     "
   
     {0}
   
     "
   
     , ex.Message);
 
   
     return
   
     ;
 }
 }
 cn.Close();
}
  
    

"