大家快来帮我看看这段代码 dropdownlist绑定 无数据显示 C# .net
SqlConnection sqlcon = new SqlConnection();
 string connstr = @"Data Source=.\SQLEXPRESS;AttachDBFilename=|DataDirectory|\xiangdan.mdf;Integrated Security=True;User Instance=True";
  sqlcon.ConnectionString = connstr;

  SqlCommand cmd = new SqlCommand();
  cmd.Connection = sqlcon;
  cmd.CommandText = "select*from xiangdan";

  SqlDataAdapter adapter = new SqlDataAdapter();
  adapter.SelectCommand = cmd;

  DataSet bown = new DataSet();
  adapter.Fill(bown);

  DataTable dt = bown.Tables["xiangdan"];
  DropDownList1.DataSource = dt;
  DropDownList1.SelectedValue = "nianji";
   
  DropDownList1.DataValueField = "xueyuan";
  DropDownList1.DataTextField = "banji"; 
  DropDownList1.DataBind();
  Response.Write("this.DropDownList1.DataTextField = 'banji'");

------解决方案--------------------

C# code

string connstr = @"Data Source=.\SQLEXPRESS;AttachDBFilename=|DataDirectory|\xiangdan.mdf;Integrated Security=True;User Instance=True";
DataSet bown = new DataSet();
using(SqlConnection sqlcon = new SqlConnection(connstr))
{
      string strSQL = "select * from xiangdan";
      using(SqlDataAdapter adapter = new SqlDataAdapter(strSQL,sqlcon))
     {
           adapter.Fill(bown);
           DropDownList1.DataSource = bown;
           DropDownList1.DataTextField = "banji"; 
           DropDownList1.DataValueField = "xueyuan";
           DropDownList1.DataBind();
           // DropDownList1.SelectedValue = "nianji";
     }
}