pass data from dropdownlist

问题:

I have been trying to pass selected data from two dropdownlist (page1.aspx) to (page2.aspx) I am not having any luck as it seems the data is not being passed when selected. Please help, this doesn't seem that difficult, but I can not get it work. On (page2.aspx) the data from the dropdownlists will be passed to a stored procedure and all results will be in a gridview.

Here is my code:

Page1.aspx

<asp:DropDownList ID="ddlState" runat="server" AutoPostBack="True" DataSourceID="SqlDataSource1" DataTextField="ST_Code" DataValueField="ST_Code" />
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:dbConnection %>"SelectCommand="SELECT [ST_Code] FROM [State]">
</asp:SqlDataSource> City:  <asp:DropDownList ID="ddlCity" runat="server" DataSourceID="SqlDataSource2" DataTextField="RS_City" DataValueField="RS_City" />
<asp:SqlDataSource ID="SqlDataSource2" runat="server" ConnectionString="<%$ ConnectionStrings:dbConnection %>"SelectCommand="ListbyStateSPROC"SelectCommandType="StoredProcedure">`
        <SelectParameters>
            <asp:ControlParameter ControlID="ddlState" Name="State" PropertyName="SelectedValue"  Type="String" />       
        </SelectParameters>
</asp:SqlDataSource>

       <asp:Button ID="Submit" runat="server" Text="Submit" />
    &nbsp;

</asp:Content>

Page1.aspx.vb

Imports System.Data
Imports System.Data.Common
Imports System.Data.SqlClient
Imports System.Web.UI.WebControls.DataGrid
Imports System.Web.UI.WebControls.DropDownList


Partial Public Class LiveEventSearch
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    End Sub

    Public Sub ddlState_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
        SqlDataSource2.SelectParameters.Clear()
        SqlDataSource2.SelectParameters.Add(New Parameter("@State", DbType.String, ddlState.SelectedValue))
        ddlCity.DataBind()


    End Sub

    Protected Sub ddlCity_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ddlCity.SelectedIndexChanged

    End Sub


    Protected Sub Submit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Submit.Click

    End Sub
End Class

Page2.aspx

 <asp:GridView ID="GridView1" runat="server" AllowSorting="True" AutoGenerateColumns="False"
        DataSourceID="SqlDataSource1" Style="z-index: 100; left: 324px; position: absolute;
        top: 226px">
        <Columns>
            <asp:BoundField DataField="Code" HeaderText="Code" ReadOnly="True" SortExpression="R_Code" />
            <asp:BoundField DataField="Name" HeaderText="Name" ReadOnly="True" SortExpression="R_Name" />
            <asp:BoundField DataField="Number" HeaderText="Number" ReadOnly="True" SortExpression="RS_Number" />
            <asp:BoundField DataField="Addr_1" HeaderText="Addr_1" ReadOnly="True" SortExpression="RS_Addr_1" />
            <asp:BoundField DataField="City" HeaderText="City" ReadOnly="True" SortExpression="RS_City" />
            <asp:BoundField DataField="State" HeaderText="State" ReadOnly="True" SortExpression="RS_State" />
            <asp:BoundField DataField="RS_Zip" HeaderText="RS_Zip" ReadOnly="True" SortExpression="RS_Zip" />
        </Columns>
    </asp:GridView>
    <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:dbConnection %>"
        SelectCommand="ListbyCityStSPROC" SelectCommandType="StoredProcedure">
        <SelectParameters>
            <asp:QueryStringParameter Name="City" QueryStringField="RS_City" Type="String" />
            <asp:QueryStringParameter Name="State" QueryStringField="ST_Code" Type="String" />
        </SelectParameters>
    </asp:SqlDataSource>

</asp:Content>

回答1:

Effectively each page in an ASP.NET application is like a single app in itself, things don't last across pages, so you either need to implement a class that keeps hold of your SQLDataSource so can call it across pages or you need to implement some way to copy the data across the pages.

You could also use the FindControl function to find the SQLDataSource across pages:

SqlDataSource sql = (SqlDataSource)Page.Master.Findcontrol("SqlDataSource1");