您应该重用SqlConnection,SqlDataAdapter和SqlCommand对象吗？

Question

我正在使用以类似于以下代码的布局编写的DAL对象.我简化了很多代码只是为了显示设置.

public class UserDatabase : IDisposable
{
    private SqlDataAdapter UserDbAdapter;
    private SqlCommand UserSelectCommand;
    private SqlCommand UserInsertCommand;
    private SqlCommand UserUpdateCommand;
    private SqlCommand UserDeleteCommand;

    private System.Data.SqlClient.SqlConnection SQLConnection; 

    public UserDatabase()
    {
        this.SQLConnection = new System.Data.SqlClient.SqlConnection(ConnectionString);
        this.UserDbAdapter= new SqlDataAdapter(); 
        this.UserDbAdapter.DeleteCommand = this.UserDeleteCommand;
        this.UserDbAdapter.InsertCommand = this.UserInsertCommand;
        this.UserDbAdapter.SelectCommand = this.UserSelectCommand;
        this.UserDbAdapter.UpdateCommand = this.UserUpdateCommand;
    }

    private bool FillUsers(DataSet UserDataSet, out int numberOfRecords)
    {
        bool success = true;

        numberOfRecords = 0;
        string errorMsg = null;

        this.UserDbAdapter.SelectCommand = this.GetUsersSelectCommand();

        numberOfRecords = UserDbAdapter.Fill(UserDataSet, UsersTableName);

        return success;
    }

    private SqlCommand GetUserSelectCommand()
    {
        if (this.UserSelectCommand==null)
            this.UserSelectCommand= new System.Data.SqlClient.SqlCommand();
        this.UserSelectCommand.CommandText = "dbo.Users_Select";
        this.UserSelectCommand.CommandType = System.Data.CommandType.StoredProcedure;
        this.UserSelectCommand.Connection = this.SQLConnection;
        this.UserSelectCommand.Parameters.Clear();
        this.UserSelectCommand.Parameters.AddRange(new System.Data.SqlClient.SqlParameter[] {
        new System.Data.SqlClient.SqlParameter("@RETURN_VALUE", System.Data.SqlDbType.Variant, 0, System.Data.ParameterDirection.ReturnValue, false, ((byte)(0)), ((byte)(0)), "", System.Data.DataRowVersion.Current, null)});

        return UserSelectCommand;
    }

还有多个其他Fill类型函数的编写方式与重用Connection对象,SqlCommands和SqlDataAdapter的方式相同.SqlDataAdapter在内部管理SqlConnection的打开和关闭.

所以我的问题是多部分.这个设计不好吗？如果是这样,为什么？

如果它不好,是否应该更改为将事物保存在更本地的范围内,如下所示:

    public bool FillUsers(DataSet UserDataSet)
    {
        using (SqlConnection conn = new SqlConnection(ConnectionString))
        {
            using (SqlCommand command = GetUsersSelectCommand())
            {
                using (SqlDataAdapter adapter = new SqlDataAdapter(command, conn))
                {
                    adapter.Fill(UserDataSet, UsersTableName);
                }
            }
        }
    }

这对于所有看起来像创建,处理,然后重新制作的功能都必须要比保留项目更糟糕.然而,这似乎是我在网上到处看到的设置.

Answer 1

不,这没有任何问题.您应该IDisposable在完成后立即处理实现的对象.

给定a SqlConnection,当您处理连接时,底层连接将简单地返回到池中.它可能不像你想象的那样"封闭".最好让连接池完成它的工作. 这是MSDN到ADO.NET连接池的链接.试图让它做的事情不是为了设计(有些人称之为优化,令人惊讶),通常是在兔子洞里旅行.

此外,在尝试优化之前,请确保已实际测量并观察到问题.(我并不是以严厉的方式表达这一点,只是为了节省你的时间).