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();
}

"