理解“使用” asp.net 4.0 中的语句 - C#

Question

这两个代码有什么区别吗？应该使用哪一个？

asp.net 4.0，c#

代码 1：

using System;
using System.Data.Sql;
using System.Data.SqlClient;
using System.Data;

public static class DbConnection
{
    public static string srConnectionString = "server=localhost;database=mydb;uid=sa;pwd=mypw;";

    public static DataSet db_Select_Query(string strQuery)
    {
        DataSet dSet = new DataSet();

        try
        {
            using (SqlConnection connection = new SqlConnection(srConnectionString))
            {
                connection.Open();
                SqlDataAdapter DA = new SqlDataAdapter(strQuery, connection);
                DA.Fill(dSet);
            }
            return dSet;
        }
        catch
        {
            if (srConnectionString.IndexOf("select Id from tblAspErrors") != -1)
            {
                using (SqlConnection connection = new SqlConnection(srConnectionString))
                {
                    connection.Open();
                    strQuery = strQuery.Replace("'", "''");
                    SqlCommand command = new SqlCommand("insert into tblSqlErrors values ('" + strQuery + "')", connection);
                    command.ExecuteNonQuery();
                }
            }
            return dSet;
        }
    }

    public static void db_Update_Delete_Query(string strQuery)
    {
        try
        {
            using (SqlConnection connection = new SqlConnection(srConnectionString))
            {
                connection.Open();
                SqlCommand command = new SqlCommand(strQuery, connection);
                command.ExecuteNonQuery();
            }
        }
        catch
        {
            strQuery = strQuery.Replace("'", "''");
            using (SqlConnection connection = new SqlConnection(srConnectionString))
            {
                connection.Open();
                SqlCommand command = new SqlCommand("insert into tblSqlErrors values ('" + strQuery + "')", connection);
                command.ExecuteNonQuery();
            }
        }
    }
}

代码 2：

using System;
using System.Data.Sql;
using System.Data.SqlClient;
using System.Data;

public static class DbConnection
{
    public static string srConnectionString = "server=localhost;database=mydb;uid=sa;pwd=mypw;";

    public static DataSet db_Select_Query(string strQuery)
    {
        DataSet dSet = new DataSet();

        try
        {
            using (SqlConnection connection = new SqlConnection(srConnectionString))
            {
                connection.Open();
                using (SqlDataAdapter DA = new SqlDataAdapter(strQuery, connection))
                {
                    DA.Fill(dSet);
                }
            }
            return dSet;
        }

        catch
        {
            using (SqlConnection connection = new SqlConnection(srConnectionString))
            {
                if (srConnectionString.IndexOf("select Id from tblAspErrors") != -1)
                {
                    connection.Open();
                    strQuery = strQuery.Replace("'", "''");

                    using (SqlCommand command = new SqlCommand("insert into tblSqlErrors values ('" + strQuery + "')", connection))
                    {
                        command.ExecuteNonQuery();
                    }
                }
            }
            return dSet;
        }
    }

    public static void db_Update_Delete_Query(string strQuery)
    {
        try
        {
            using (SqlConnection connection = new SqlConnection(srConnectionString))
            {
                connection.Open();
                using (SqlCommand command = new SqlCommand(strQuery, connection))
                {
                    command.ExecuteNonQuery();
                }
            }
        }
        catch
        {
            strQuery = strQuery.Replace("'", "''");
            using (SqlConnection connection = new SqlConnection(srConnectionString))
            {
                connection.Open();
                using (SqlCommand command = new SqlCommand("insert into tblSqlErrors values ('" + strQuery + "')", connection))
                {
                    command.ExecuteNonQuery();
                }
            }
        }
    }
}

Answer 1

如果您有 ReSharper 为您做这件事或者愿意手动下载它们，您可以查看 SqlCommand 和 SqlDataAdapter 的源代码，看看它们的 Dispose() 方法是否有效实际上做任何事情。如果没有，那么省略它们周围的 using 语句可能是安全的。

Answer 2

您应该考虑的是，using 子句用于确保在 using 子句的括号内使用的对象正确地处理到内存中。

所以，我认为你应该使用第二个代码示例。