<%@ Page Language="C#" %>
<%@ Import Namespace="System.Data" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">
  ICollection CreateDataSource()
  {
    DataTable dt = new DataTable();
    DataRow dr;
    dt.Columns.Add(new DataColumn("id", typeof(Int32)));
    dt.Columns.Add(new DataColumn("text", typeof(string)));
    for (int i = 0; i < 6; i++)
    {
      dr = dt.NewRow();
      dr[0] = i;
      dr[1] = "列表项目 " + i.ToString();
      dt.Rows.Add(dr);
    }
    DataView dv = new DataView(dt);
    return dv;
  }

  public class GridViewTemplate : ITemplate
  {
    private DataControlRowType templateType;
    private string columnName;

    public GridViewTemplate( DataControlRowType type, string colname )
    {
      templateType = type;
      columnName = colname;
    }

    public void InstantiateIn( System.Web.UI.Control container )
    {
      switch (templateType)
      {
        case DataControlRowType.Header:
          Literal lc = new Literal();
          lc.Text = columnName;         
          container.Controls.Add(lc);         
          break;
        case DataControlRowType.DataRow:
          DropDownList drr = new DropDownList();
          drr.ID = "dropdown";
          drr.AppendDataBoundItems = true;
          drr.Items.Add(new ListItem("-----请选择------",""));
          drr.Items.Add(new ListItem("AA", "a"));
          drr.Items.Add(new ListItem("BB", "b"));
          drr.Items.Add(new ListItem("CC", "c"));
          container.Controls.Add(drr);
          break;
        default:
         break;
      }
    }
  }
 
  protected void Page_Load(object sender, EventArgs e)
  {
    if (!IsPostBack)
    {
      TemplateField customField = new TemplateField();
      customField.ShowHeader = true;
      customField.HeaderTemplate = new GridViewTemplate(DataControlRowType.Header, "动态添加列");
      customField.ItemTemplate = new GridViewTemplate(DataControlRowType.DataRow, "");
      GridView1.Columns.Add(customField);
      GridView1.DataSource = CreateDataSource();
      GridView1.DataBind();
    }
  }

  protected void GridView1_RowDataBound( object sender, GridViewRowEventArgs e )
  {
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
      DataRowView gv = (DataRowView)e.Row.DataItem;
      int itemSeleted = Int32.Parse(gv.Row["id"].ToString()) > 3 ? 0 : Int32.Parse(gv.Row["id"].ToString());

      DropDownList dr = (DropDownList)e.Row.FindControl("dropdown");
      dr.SelectedIndex = itemSeleted;
    }
  }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
  <title>例子</title>
</head>
<body>
<form id="form1" runat="server">
  <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False" OnRowDataBound="GridView1_RowDataBound">
    <Columns>
      <asp:BoundField HeaderText="标题"  DataField="text"/>
    </Columns>
  </asp:GridView>
</form>
</body>
</html>