Postback重置GridView中DropdownList的selectedValue

我的网格视图有两列-DropDownList&文本框。DDL由数据表进行数据绑定。DDL的SelectedIndex Change将填充其文本框，并添加新行。所有这些都可以正常工作，但当添加新行时，前几行的DDL的选定值将重置为0索引。不过，文本框值保持不变。添加新行时，如何保留DDL选定的值。

例如，如果我从第1行的下拉列表中选择"abc"，它将填充其文本字段，并添加一个新行。但随着回发的发生，abc在第1行ddl:中不会保持选中状态

登录电话1 1234567892.

ASPX:

<asp:GridView ID="gvCommissions" runat="server"
 OnRowDataBound="gvCommissions_RowDataBound">
 <Columns>
  <asp:TemplateField HeaderText="LOGIN" ItemStyle-Width="29%">
   <ItemTemplate>
    <asp:DropDownList ID="ddlLogin" runat="server" Width="98%" 
     DataTextField="login" DataValueField="id"
     OnSelectedIndexChanged="ddlLogin_SelectedIndexChanged" AutoPostBack="true" >
     </asp:DropDownList>
   </ItemTemplate>
  </asp:TemplateField>
  <asp:TemplateField HeaderText="PHONE" ItemStyle-Width="12%">
   <ItemTemplate>
    <asp:TextBox ID="txtPhone" runat="server" Width="98%" 
    Text='<%# Eval("phone")%>' Enabled="false"></asp:TextBox>
   </ItemTemplate>
  </asp:TemplateField>
 </Columns>
</asp:GridView>

代码隐藏：

protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
         //Get values from DB, store to a datatable and then to a viewstate               
            GetAgentDetails();
         //Adds an empty row to grid                
            SetInitialRow(); 
        }            
    }
private void AddNewRow()
    {
      //Create a datatable 
      dtCurrentData = new DataTable();
      dtCurrentData.Columns.Add("phone");
//Store values of each row to a new datarow. Add all rows to datatable
      foreach (GridViewRow gvRow in gvCommissions.Rows)
        {
          DataRow drcurrentrow = dtCurrentData.NewRow();                      
          drcurrentrow["phone"] = ((TextBox)gvRow.FindControl("txtphone")).Text;
          dtCurrentData.Rows.Add(drcurrentrow);
        }
      //create an empty datarow and also add it to the new datatable.
        DataRow dr = dtCurrentData.NewRow();
        dr["phone"] = "";
        dtCurrentData.Rows.Add(dr);
     //Bind the new datatable to the grid
       gvCommissions.DataSource = dtCurrentData;
       gvCommissions.DataBind();
   }
protected void gvCommissions_RowDataBound(object sender, GridViewRowEventArgs e)
    {
     if (e.Row.RowType == DataControlRowType.DataRow)
      {
        DropDownList ddl = (DropDownList)e.Row.FindControl("ddlLogin");
        dtAgents = (DataTable)ViewState["AgentsTable"];
        ddl.DataSource = dtAgents;
        ddl.DataBind();
        ddl.Items.Insert(0, "");
      }            
    }

private void AddNewRow()
{
  //Create a datatable 
  dtCurrentData = new DataTable();
  dtCurrentData.Columns.Add("phone");
  //new column for dropdown index
  dtCurrentData.Columns.Add("ddlIndex");
//Store values of each row to a new datarow. Add all rows to datatable
  foreach (GridViewRow gvRow in gvCommissions.Rows)
    {
      DataRow drcurrentrow = dtCurrentData.NewRow();                      
      drcurrentrow["phone"] = ((TextBox)gvRow.FindControl("txtphone")).Text;
      //get dropdown index
      drcurrentrow["ddlIndex"] = ((DropDownList)gvRow.FindControl("ddlLogin")).SelectedIndex;
      dtCurrentData.Rows.Add(drcurrentrow);
    }
  //create an empty datarow and also add it to the new datatable.
    DataRow dr = dtCurrentData.NewRow();
    dr["phone"] = "";
    //initial drop down index
    dr["ddlIndex"] = 0;
    dtCurrentData.Rows.Add(dr);
    //save to the viewstate like your AgentsTable
    ViewState["CurrentData"] = dtCurrentData;
 //Bind the new datatable to the grid
   gvCommissions.DataSource = dtCurrentData;
   gvCommissions.DataBind();
}
protected void gvCommissions_RowDataBound(object sender, GridViewRowEventArgs e)
{
 if (e.Row.RowType == DataControlRowType.DataRow)
  {
    DropDownList ddl = (DropDownList)e.Row.FindControl("ddlLogin");
    dtAgents = (DataTable)ViewState["AgentsTable"];
    ddl.DataSource = dtAgents;
    ddl.DataBind();
    ddl.Items.Insert(0, "");
    //get the dropdown index from CurrentData
    //use the current gridview's row index, since it matches the datatable
    if (ViewState["CurrentData"] != null)
    {
     DataTable dtCurrentData = (DataTable)ViewState["CurrentData"];
     ddl.SelectedIndex = Convert.ToInt32(dtCurrentData.Rows[e.Row.RowIndex]["ddlIndex"]);
    }
  }            
}