国产一级a片免费看高清,亚洲熟女中文字幕在线视频,黄三级高清在线播放,免费黄色视频在线看

示例數(shù)據(jù)庫字段名字段類型允許空字段說明IDuniqueidentifier表主鍵字段UserNamevarchar(50)留言用戶名PostTimedatetime留言時間Messagevarchar(400)√留言內(nèi)容IsRepliedbit留言是否回復(fù)Replyvarchar(400)√留言管理員回復(fù)在數(shù)據(jù)庫中創(chuàng)建一個名為GuestBook的數(shù)據(jù)庫，在里面創(chuàng)建一個tbGuestBook的表，結(jié)構(gòu)如上表。生成實(shí)體類右鍵點(diǎn)擊網(wǎng)站項目，選擇添加新項，然后選擇“Linq to sql Classes”，命名為GuestBook。然后打開App_Code里面的GuestBook.dbml。設(shè)計視圖上的文字提示你可以從服務(wù)器資源管理器或者攻擊箱拖動項到設(shè)計界面上來創(chuàng)建實(shí)體類。那么，我們就在服務(wù)器資源管理器中創(chuàng)建一個指向GuestBook數(shù)據(jù)庫的數(shù)據(jù)連接，然后把tbGuestBook表拖動到GuestBook.dbml的設(shè)計視圖上，按CTRL+S保存。打開GuestBook.designer.cs可以發(fā)現(xiàn)系統(tǒng)自動創(chuàng)建了GuestBook數(shù)據(jù)庫中tbGuestBook表的映射，如下圖：簡易留言簿現(xiàn)在，我們就可以使用Linq to sql完成簡易留言簿了。實(shí)現(xiàn)以下功能：l         發(fā)表留言（增）l         查看留言（查）l         管理員回復(fù)留言（改）l         管理員刪除留言（刪除）首先，創(chuàng)建一個Default.aspx，在頁面上加入一些控件：<div>姓名<asp:TextBox ID="tb_UserName" runat="server"></asp:TextBox><br /><br />留言<asp:TextBox ID="tb_Message" runat="server" Height="100px" TextMode="MultiLine" Width="300px"></asp:TextBox><br /><br /><asp:Button ID="btn_SendMessage" runat="server" Text="發(fā)表留言" OnClick="btn_SendMessage_Click" /><br /><br /><asp:Repeater ID="rpt_Message" runat="server"><ItemTemplate><table width="600px" style="border:solid 1px #666666; font-size:10pt; background-color:#f0f0f0"><tr><td align="left" width="400px"><%# Eval("Message")%></td><td align="right" width="200px"><%# Eval("PostTime")%> - <%# Eval("UserName")%></td></tr><tr><td colspan="2" align="right"><hr width="300px" />管理員回復(fù)：<%# Eval("IsReplied").ToString() == "False" ? "暫無" : Eval("Reply")%></td></tr></table><br/></ItemTemplate></asp:Repeater></div>你可能很難想象，使用Linq to sql進(jìn)行數(shù)據(jù)訪問會是這么簡單，后臺代碼：public partial class _Default : System.Web.UI.Page{GuestBookDataContext ctx = new GuestBookDataContext("server=xxx;database=GuestBook;uid=xxx;pwd=xxx");protected void Page_Load(object sender, EventArgs e){if (!IsPostBack){SetBind();}}protected void btn_SendMessage_Click(object sender, EventArgs e){tbGuestBook gb = new tbGuestBook();gb.ID = Guid.NewGuid();gb.UserName = tb_UserName.Text;gb.Message = tb_Message.Text;gb.IsReplied = false;gb.PostTime = DateTime.Now;ctx.tbGuestBooks.Add(gb);ctx.SubmitChanges();SetBind();}private void SetBind(){rpt_Message.DataSource = from gb in ctx.tbGuestBooks orderby gb.PostTime descending select gb;rpt_Message.DataBind();}}前面創(chuàng)建Linq to sql Classes的時候我們輸入名字GuestBook，系統(tǒng)就為我們自動創(chuàng)建了GuestBookDataContext（你也可以在GuestBook.Designer.cs中找到類定義）。在綁定的時候我們使用查詢句法查詢留言表中所有留言，按照發(fā)表時間倒序（天哪？這是數(shù)據(jù)訪問嗎？好像僅僅定義了一句SQL?。?。在發(fā)表留言按鈕中，我們?yōu)橐粋€tbGuestBook賦值，然后把它加入留言表，再提交更改，就這樣完成了記錄的插入。運(yùn)行效果如下圖：然后，再創(chuàng)建一個Admin.aspx，前臺代碼如下：<div><asp:Repeater ID="rpt_Message" runat="server" OnItemCommand="rpt_Message_ItemCommand"><ItemTemplate><table width="600px" style="border:solid 1px #666666; font-size:10pt; background-color:#f0f0f0"><tr><td align="left" width="400px"><%# Eval("Message")%></td><td align="right" width="200px"><%# Eval("PostTime")%> - <%# Eval("UserName")%></td></tr><tr><td colspan="2" align="right"><hr width="300px" /><asp:Button ID="btn_DeleteMessage" runat="server" Text="刪除留言" CommandName="DeleteMessage" CommandArgument='<%# Eval("ID")%>'/>管理員回復(fù)：<asp:TextBox runat="server" ID="tb_Reply" TextMode="MultiLine" Width="300px" Text='<%# Eval("Reply")%>'/><asp:Button ID="btn_SendReply" runat="server" Text="發(fā)表回復(fù)" CommandName="SendReply" CommandArgument='<%# Eval("ID")%>'/></td></tr></table><br/></ItemTemplate></asp:Repeater></div>后臺代碼：public partial class Admin : System.Web.UI.Page{GuestBookDataContext ctx = new GuestBookDataContext("server=xxx;database=GuestBook;uid=xxx;pwd=xxx");protected void Page_Load(object sender, EventArgs e){if (!IsPostBack){SetBind();}}private void SetBind(){rpt_Message.DataSource = from gb in ctx.tbGuestBooks orderby gb.PostTime descending select gb;rpt_Message.DataBind();}protected void rpt_Message_ItemCommand(object source, RepeaterCommandEventArgs e){if (e.CommandName == "DeleteMessage"){StreamWriter sw = new StreamWriter(Server.MapPath("log.txt"), true);ctx.Log = sw;tbGuestBook gb = ctx.tbGuestBooks.Single(b => b.ID == new Guid(e.CommandArgument.ToString()));ctx.tbGuestBooks.Remove(gb);ctx.SubmitChanges();SetBind();sw.Close();}if (e.CommandName == "SendReply"){StreamWriter sw = new StreamWriter(Server.MapPath("log.txt"), true);ctx.Log = sw;tbGuestBook gb = ctx.tbGuestBooks.Single(b => b.ID == new Guid(e.CommandArgument.ToString()));gb.Reply = ((TextBox)e.Item.FindControl("tb_Reply")).Text;gb.IsReplied = true;ctx.SubmitChanges();SetBind();sw.Close();}}}運(yùn)行效果如下圖：在這里，我們通過Single方法獲取一條記錄，也就是一個tbGuestBook實(shí)例，更新了一些屬性后保存也就完成了改這個操作。刪除操作更簡單，只需要從表中移除對象。你是不是覺得好像不是在操作數(shù)據(jù)庫，像在操作內(nèi)存中的對象。由于寫了日志，看看改和刪操作會是怎么樣的SQL？UPDATE [dbo].[tbGuestBook]SET [IsReplied] = @p4, [Reply] = @p5WHERE ([ID] = @p0) AND ([UserName] = @p1) AND ([PostTime] = @p2) AND ([Message] = @p3) AND (NOT ([IsReplied] = 1)) AND ([Reply] IS NULL)-- @p0: Input Guid (Size = 0; Prec = 0; Scale = 0) [00000000-0000-0000-0000-000000000000]-- @p1: Input String (Size = 4; Prec = 0; Scale = 0) [ghgh]-- @p2: Input DateTime (Size = 0; Prec = 0; Scale = 0) [2007-8-16 10:20:09]-- @p3: Input String (Size = 3; Prec = 0; Scale = 0) [ghj]-- @p4: Input Boolean (Size = 0; Prec = 0; Scale = 0) [True]-- @p5: Input String (Size = 3; Prec = 0; Scale = 0) [qqq]-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1DELETE FROM [dbo].[tbGuestBook] WHERE ([ID] = @p0) AND ([UserName] = @p1) AND ([PostTime] = @p2) AND ([Message] = @p3) AND (NOT ([IsReplied] = 1)) AND ([Reply] = @p4)-- @p0: Input Guid (Size = 0; Prec = 0; Scale = 0) [158ec941-13ff-4093-bd8b-9fceae152171]-- @p1: Input String (Size = 2; Prec = 0; Scale = 0) [44]-- @p2: Input DateTime (Size = 0; Prec = 0; Scale = 0) [2007-8-16 9:56:19]-- @p3: Input String (Size = 2; Prec = 0; Scale = 0) [44]-- @p4: Input String (Size = 3; Prec = 0; Scale = 0) [222]-- Context: SqlProvider(Sql2005) Model: AttributedMetaModel Build: 3.5.20706.1今天就講到這里，下次將系統(tǒng)介紹查詢句法。100(請您對文章做出評價)