在ASP.NET中實現Model-View-Controller模式（四）

模型-視圖-控制器分離的重構

為了解決上面所遺留的問題，你必須將模型與控制器角色分離。

視圖的實現代碼與前部分相同。

模型

下面的代碼例子使模型角色僅僅依賴于數據庫，而不包含任何與視圖相依賴的代碼。

using System;

using System.Collections;

using System.Data;

using System.Data.SqlClient;



public class DatabaseGateway

{

public static DataSet GetRecordings()

{

String selectCmd = "select * from Recording";



SqlConnection myConnection =

new SqlConnection(

"server=(local);database=recordings;Trusted_Connection=yes");

SqlDataAdapter myCommand = new SqlDataAdapter(selectCmd, myConnection);



DataSet ds = new DataSet();

myCommand.Fill(ds, "Recording");

return ds;

}



public static DataSet GetTracks(string recordingId)

{

String selectCmd =

String.Format(

"select * from Track where recordingId = {0} order by id",

recordingId);



SqlConnection myConnection =

new SqlConnection(

"server=(local);database=recordings;Trusted_Connection=yes");

SqlDataAdapter myCommand = new SqlDataAdapter(selectCmd, myConnection);



DataSet ds = new DataSet();

myCommand.Fill(ds, "Track");

return ds;

}



現在的代碼只依賴于數據庫，這個類是一個優秀的數據庫的通道，它持有訪問表或視圖的所用的SQL語句，其它的代碼調用一些方法來完成與數據庫的交互。

控制器

這種重構方式利用代碼隱藏機制，在負責數據訪問的模型部分相對獨立的情況下，由控制器負責事件與方法的控制工作。模型的任務很明確的，它僅返回一個DataSet對象。這種實現方式就像視圖代碼一樣，不依賴于數據是如何從數據庫中返回的。

using System;

using System.Data;

using System.Collections;

using System.Web.UI.WebControls;



public class Solution : System.Web.UI.Page

{

protected System.Web.UI.WebControls.Button submit;

protected System.Web.UI.WebControls.DataGrid MyDataGrid;

protected System.Web.UI.WebControls.DropDownList recordingSelect;



private void Page_Load(object sender, System.EventArgs e)

{

if(!IsPostBack)

{

DataSet ds = DatabaseGateway.GetRecordings();

recordingSelect.DataSource = ds;

recordingSelect.DataTextField = "title";

recordingSelect.DataValueField = "id";

recordingSelect.DataBind();

}

}



void SubmitBtn_Click(Object sender, EventArgs e)

{

DataSet ds =

DatabaseGateway.GetTracks(

(string)recordingSelect.SelectedItem.Value);



MyDataGrid.DataSource = ds;

MyDataGrid.DataBind();

}



#region Web Form Designer generated code

override protected void OnInit(EventArgs e)

{

//

// CODEGEN: This call is required by the ASP.NET Web Form Designer.

//

InitializeComponent();

base.OnInit(e);

}



/// <summary>

/// Required method for Designer support - do not modify

/// the contents of this method with the code editor.

/// </summary>

private void InitializeComponent()

{

this.submit.Click += new System.EventHandler(this.SubmitBtn_Click);

this.Load += new System.EventHandler(this.Page_Load);



}

#endregion

}