ASP.NET与数据库相关技巧

一、取得数据表 i 行 j 列的值   

     //建立并打开数据库连接
    oledbconnection conn=new oledbconnection();
    conn.connectionstring=strconnectionstring;//strconnectionstring为数据库连接字符串
    conn.open();

    string sql="select * from newsclass order by classid desc";
    string x; 
    dataset ds=new dataset();
    oledbdataadapter da=new oledbdataadapter(sql,conn);  
    da.fill(ds,"newstable");
    datatable dt=ds.tables["newstable"]; 
    x=dt.rows[i][1].tostring()//数据表i行j列的值  
    conn.close();

二、将数据读入dropdownlist

（1）  dropdownlist中添加数据

  //建立并打开数据库连接
    oledbconnection conn=new oledbconnection();
    conn.connectionstring=strconnectionstring;//strconnectionstring为数据库连接字符串
    conn.open();

    string sql="select * from newsclass order by classid desc";
    //建立数据集
    dataset ds=new dataset();
    oledbdataadapter da=new oledbdataadapter(sql,conn);  
    da.fill(ds,"newstable");
    this.dropdownlist1.datasource=ds;
    this.dropdownlist1.datatextfield = "classname";//text值
    this.dropdownlist1.datavaluefield = "classid";//value值
    this.dropdownlist1.databind();
    
    conn.close();

（2）选中dropdownlist的某项

this.dropdownlist1.items.findbyvalue(dr["classid"].tostring().trim()).selected=true;//dr为datarow

三、分类编码检索出相应的分类名称并在datagrid中显示

（1）.aspx中的代码（classid为分类编码）：

    <asp:templatecolumn headertext="类 别">
         <itemtemplate>
          <asp:label id=lblclass runat="server" text='<%# getclassname(convert.toint32(databinder.eval(container, "dataitem.classid"))) %>'>
          </asp:label>
         </itemtemplate>
        </asp:templatecolumn>

（2）c#代码：

 /// <summary>
  /// "分类"列根据数字返回文字
  /// </summary>
  /// <param name="ispassed"></param>
  /// <returns></returns>
  public string  getclassname(int classid)
  {
   oledbconnection conn=new oledbconnection();
   conn.connectionstring=strconnectionstring;
   conn.open();

   string sql="select * from newsclass where classid="+classid;
   dataset ds=new dataset();
   oledbdataadapter da=new oledbdataadapter(sql,conn);
   da.fill(ds,"classtable");
   datatable dt=ds.tables["classtable"];
   string strclassname=dt.rows[0]["classname"].tostring();
   conn.close();

   return strclassname;//返回 classid对应的classname
  }