选择dropdownlist后，关联的gridview有时候变有时候不随着变

dropdownlist1绑定到sqldatasource1从数据库读取单位名称
dropdownlist2绑定到sqldatasource2从数据库读取部门名称
gridview1绑定到sqldatasource3从数据库读取员工名称sqldatasource2关联到dropdownlist1
sqldatasource3关联到dropdownlist2现在的问题是：
选择部门后，员工表格肯定随着变
选择单位后，部门列表肯定随着变，但员工表格有时候随着变，有时候不随着变，奇怪了

解决方案 »

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现在有问题的代码如下：<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="RenShi_Default" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>无标题页</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
          
        <br />
        <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" DataSourceID="SqlDataSource1"
            DataTextField="Name" DataValueField="Id" AppendDataBoundItems="True">
        </asp:DropDownList>
        <asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="True" DataSourceID="SqlDataSource2"
            DataTextField="Name" DataValueField="Id">
        </asp:DropDownList><br />
        <asp:GridView ID="GridView1" runat="server" AllowPaging="True" AutoGenerateColumns="False"
            DataSourceID="SqlDataSource3" AllowSorting="True" Height="1px" Width="308px" DataKeyNames="Id">
            <Columns>
                <asp:BoundField DataField="Id" HeaderText="Id" InsertVisible="False" ReadOnly="True"
                    SortExpression="Id" />
                <asp:BoundField DataField="Name" HeaderText="Name" SortExpression="Name" />
                <asp:BoundField DataField="Sex" HeaderText="Sex" SortExpression="Sex" />
                <asp:BoundField DataField="Birthday" HeaderText="Birthday" SortExpression="Birthday" />
            </Columns>
        </asp:GridView>
        <br />
        <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:MyDB %>"
            SelectCommand="SELECT * FROM [unit]"></asp:SqlDataSource>
        <asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:MyDB %>"
            SelectCommand="SELECT * FROM [department] where unitid=@unitid">
            <SelectParameters>
                <asp:ControlParameter ControlID="DropDownList1" Name="unitid" PropertyName="SelectedValue" />
            </SelectParameters>
        </asp:SqlDataSource>
        <asp:SqlDataSource ID="SqlDataSource3" runat="server" ConnectionString="<%$ ConnectionStrings:MyDB %>"
            SelectCommand="SELECT Id, Name, Sex, Birthday FROM teacher WHERE (DepartmentId = @departmentid)">
            <SelectParameters>
                <asp:ControlParameter ControlID="DropDownList2" Name="departmentid" PropertyName="SelectedValue" />
            </SelectParameters>
        </asp:SqlDataSource>
    </div>
    </form>
</body>
</html>
我自己解决这个问题了，增加
protected void DropDownList2_PreRender(object sender, EventArgs e)
{
GridView1.DataBind();
}
就可以了。