LINQ学习记录

今天用LINQ做了一个小东西（新闻系统,用Aspnetpager控件分页），发觉LINQ真是好东西。都不要写啥代码了。重要代码如下：

 BLL代码：

 using System;using System.Data;using System.Configuration;using System.Linq;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.HtmlControls;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Xml.Linq;/// <summary>///NewsBll 的摘要说明/// </summary>public class NewsBll{ NewsDataContext ns = new NewsDataContext();public NewsBll(){////TODO: 在此处添加构造函数逻辑//} /// <summary> /// 获取所有新闻 /// </summary> /// <returns></returns> public IQueryable GetNewsList() { var newslist = from list in ns.NewsTable select list; return newslist; } /// <summary> /// 返回一条新闻 /// </summary> /// <param name="id">新闻ID</param> /// <returns>返回新闻的所有内容</returns> public NewsTable GetSingleNews(int id) { NewsTable singlenews = ns.NewsTable.Single(news => news.ID == id); return singlenews; } /// <summary> /// 插入新闻 /// </summary> /// <param name="model">所有字段</param> /// <returns>返回操作的结果</returns> public bool InsertNews(NewsTable model) { NewsTable nt = new NewsTable(); try { nt.NewsTitle = model.NewsTitle; nt.NewsInfo = model.NewsInfo; nt.AddTime = System.DateTime.Now; ns.NewsTable.InsertOnSubmit(nt);//执行插入操作 ns.SubmitChanges(System.Data.Linq.ConflictMode.ContinueOnConflict); return true; } catch { return false; } } /// <summary> /// 更新数据 /// </summary> /// <param name="model"></param> /// <returns></returns> public bool UpdateNews(NewsTable model) { NewsTable nt = new NewsTable(); try { var sing = ns.NewsTable.Single(o => o.ID == model.ID); sing.NewsTitle = model.NewsTitle; sing.NewsInfo = model.NewsInfo; sing.AddTime = System.DateTime.Now;//修改时间 ns.SubmitChanges(); return true; } catch { return false; } } /// <summary> /// 删除新闻 /// </summary> /// <param name="id">新闻ID</param> /// <returns></returns> public bool DeleteNews(int id) { try { NewsTable news = ns.NewsTable.Single(newstable => newstable.ID == id); ns.NewsTable.DeleteOnSubmit(news); ns.SubmitChanges(); return true; } catch { return false; } } /// <summary> /// 分页获取 /// </summary> /// <param name="startIndex"></param> /// <param name="pageSize"></param> /// <returns></returns> public IQueryable GetNewsByPage(int startIndex, int pageSize) { var news = from newstable in ns.NewsTable orderby newstable.ID descending select newstable;//如果只需要其中的某些字段则 select new { n.Id, n.NewTitle, n.NewContext, n.NewImage, n.NewDate } //this.GridView1.DataSource = (from n in db.News //orderby n.Id descending //select new { n.Id, n.NewTitle, n.NewContext, n.NewImage, n.NewDate }).Skip(pagesize * pageindex).Take(pagesize); return news.Skip(startIndex*pageSize).Take(pageSize); }}

AddNews.aspx.cs:

using System;using System.Collections;using System.Configuration;using System.Data;using System.Linq;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.HtmlControls;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Xml.Linq;public partial class AddNews : System.Web.UI.Page{ NewsDataContext ns = new NewsDataContext(); NewsTable model = new NewsTable(); NewsBll nb = new NewsBll(); protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { if (Request.QueryString["ID"] == null) { btnadd.Text = "添加新闻"; } else { btnadd.Text = "修改新闻"; GetInfo(); } } } /// <summary> /// 添加或修改新闻 /// </summary> /// <param name="sender"></param> /// <param name="e"></param> protected void click(object sender, EventArgs e) { model.NewsTitle = txttitle.Text.ToString(); model.NewsInfo = txtinfo.Text.ToString(); if (btnadd.Text == "添加新闻") { if (nb.InsertNews(model) == true) { Response.Write("<mce:script type="text/javascript"><!--alert('添加成功！');window.location.href='Default.aspx';// --></mce:script></script>"); } } else if (btnadd.Text == "修改新闻") { model.ID = Convert.ToInt32(Request.QueryString["ID"]); if (nb.UpdateNews(model) == true) { Response.Write("<mce:script type="text/javascript"><!--alert('修改成功！');window.location.href='Default.aspx';// --></mce:script></script>"); } } } /// <summary> /// 获取需要修改的新闻内容 /// </summary> public void GetInfo() { model=nb.GetSingleNews(Convert.ToInt32(Request.QueryString["ID"])); txttitle.Text = model.NewsTitle; txtinfo.Text = model.NewsInfo; }}

新闻列表页面CS代码：

using System;using System.Configuration;using System.Data;using System.Linq;using System.Web;using System.Web.Security;using System.Web.UI;using System.Web.UI.HtmlControls;using System.Web.UI.WebControls;using System.Web.UI.WebControls.WebParts;using System.Xml.Linq;public partial class _Default : System.Web.UI.Page { NewsBll nsbl = new NewsBll(); NewsDataContext ns = new NewsDataContext(); protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { Bind(); } } /// <summary> /// 不分页 /// </summary> public void BindRepeater() { this.rptReplyAndDel.DataSource = nsbl.GetNewsList(); this.rptReplyAndDel.DataBind(); } /// <summary> /// 分页显示 /// </summary> public void Bind() { AspNetPager1.RecordCount = ns.NewsTable.Count(); this.rptReplyAndDel.DataSource= nsbl.GetNewsByPage(AspNetPager1.CurrentPageIndex-1, AspNetPager1.PageSize); this.rptReplyAndDel.DataBind(); } /// <summary> /// 分页事件 /// </summary> /// <param name="src"></param> /// <param name="e"></param> protected void AspNetPager1_PageChanged(object src, EventArgs e) { Bind(); } /// <summary> /// 截取字符 /// </summary> /// <param name="str"></param> /// <returns></returns> protected string FormatString(string str) { if (str.Length > 30) { str = str.Substring(0, 30) + "......"; } return str; } /// <summary> /// 删除事件 /// </summary> /// <param name="source"></param> /// <param name="e"></param> protected void rptReplyAndDel_ItemCommand(object source, RepeaterCommandEventArgs e) { int id = Convert.ToInt32(e.CommandArgument); if (e.CommandName == "delete") { if (nsbl.DeleteNews(id)) { Page.RegisterStartupScript("", "<mce:script type="text/javascript"><!--alert('删除成功！')// --></mce:script>"); } else { Page.RegisterStartupScript("", "<mce:script type="text/javascript"><!--alert('删除失败！')// --></mce:script>"); } Bind(); } }}

因为刚接触LINQ，还请各位高手指教指教