dropdownlist添加一项

drp_sales1.Items.Insert(0, new ListItem("", ""));

 ddlCategory.Items.Add(new ListItem("All", "-1"));

dropdownlist绑定失效

drp_paylist.SelectedValue = dt.Rows[0]["pay_term"].ToString();

 drp_paylist.Items.FindByText(dt.Rows[0]["pay_term"].ToString()).Selected = true;

dropdownlist与gridview（repeater）联动查询

1,AutoPostBack="true"

2.SelectedIndexChanged事件

3.drp，gridview的绑定text，value顺序

<asp:DropDownList ID="drp_sales" Width="220px" AutoPostBack="true" CssClass="easyui-combobox" runat="server" OnSelectedIndexChanged="drp_sales_SelectedIndexChanged"></asp:DropDownList>