asp.net DropdownList动态绑定的两种方法

asp教程.net dropdownlist动态绑定的两种方法
动态绑定方法一：动态绑定数据库教程中的字段。

sqlconnection conn = utilitysqlclass.operatedatabase.returnconn();
string strsql = "select * from companytype";
sqldataadapter ada = new sqldataadapter(strsql, conn);
dataset ds = new dataset();
ada.fill(ds, "companytype");
dropdownlist1.datasource = ds.tables["companytype"].defaultview;
dropdownlist1.datavaluefield = ds.tables["companytype"].columns[1].columnname;
dropdownlist1.datatextfield = ds.tables["companytype"].columns[1].columnname;
dropdownlist1.databind();
ds.dispose();

动态绑定方法二：利用dropdownlist.items.add方法。

protected void page_load(object sender, eventargs e)
{
if (!ispostback)
{
sqlconnection conn = utilitysqlclass.operatedatabase.returnconn();
try
{
conn.open();
this.dropdownlist1.items.add("");
string strsql = "select companytype from companytype";
sqlcommand com = new sqlcommand(strsql, conn);
sqldatareader dr = com.executereader();
while (dr.read())
{
this.dropdownlist1.items.add(dr["companytype"].tostring());
}
}
catch (exception ex)
{
response.write("<scirpt>alert('" + ex.message.tostring() + "')</script>");
}
finally
{
conn.close();
}
}
}

第一种方法：

        string connstring = configurationsettings.apps教程ettings["connectionstring"];
         //创建一个sqlconnection
         sqlconnection conn = new sqlconnection( connstring );      

         string sql_select = "select id, itemname from ddlitem order by id desc";

         //构造一个sqldataadapter

         sqldataadapter myadapter = new sqldataadapter( sql_select, conn);

         //开始读取数据

         conn.open();

         dataset dataset = new dataset();

         myadapter.fill( dataset,"table1" );

         conn.close();

         //开始绑定dropdownlist

         //指定dropdownlist使用的数据源

         dropdownlist1.datasource = dataset.tables["table1"].defaultview;

         //指定dropdownlist使用的表里的那些字段

         dropdownlist1.datatextfield = "itemname"; //dropdownlist的text的字段

         dropdownlist1.datavaluefield = "id";//dropdownlist的value的字段

         dropdownlist1.databind();

第二种方法：
     

   con.open();
        sqlcommand cmd = new sqlcommand(strsql,con);
        sqldatareader dr = cmd.executereader();
        while (dr.read())
        {     
            dropdownlist1.items.add(new listitem(dr["status"].tostring(), dr["status_id"].tostring()));
        }