asp.net入门来一遍----数据存取

下面是对xml,access,数据存取
protected dataset loadmypbdata()
    {
        string sourcexml = server.mappath("phone.xml");
        dataset dataset = new dataset();
        try
        {
            dataset.readxml(sourcexml);
        }
        catch (exception e)
        {
           
            dataset = null;
        }
        return dataset;
    }

    void page_load(object sender, eventargs e)
    {
        if (!(page.ispostback))
        {
            gridv.datasource = loadmypbdata();
            gridv.databind();
        }
    }
-------------------------------
string strsql="data source=127.0.0.1;initial catalog=dotnet;persist security info=true;user id=sa;password=1234;packet size=4096";
sqlconnection myconn = new sqlconnection(strsql);
myconn.open();
string commsql = "select * from gbook order by id desc";
sqldataadapter adp = new sqldataadapter(commsql,myconn);
dataset ds = new dataset();
adp.fill(ds);
datagrid1.datasource = ds;
datagrid1.databind();
myconn.close();
---------------------------------------
  if(!ispostback) 
   {
   oledbconnection myconnection =new oledbconnection("provider=microsoft.jet.oledb.4.0;data source="+server.mappath("new.mdb"));  
   oledbdataadapter mycommand=new oledbdataadapter("select id,typename from bb ",myconnection);   
   dataset ds= new dataset();  
   mycommand.fill(ds,"bb");  
   dropdownlist2.datasource = ds.tables["bb"].defaultview;    
   dropdownlist2.datatextfield = "typename";  
   dropdownlist2.datavaluefield = "id";  
   dropdownlist2.databind();