Question

我有这段代码，我正在尝试从下拉框中执行sql查询。

<html>
    <body>
        <form id="form1" runat="server">
            <asp:DropDownList ID="DropDownList1" runat="server"
                DataSourceID="SqlDataSource1" DataTextField="a" DataValueField="a">
            </asp:DropDownList>
            <asp:SqlDataSource ID="SqlDataSource1" runat="server"
                ConnectionString="<%$ ConnectionStrings:DB_firstConnectionString7 %>"
                SelectCommand="SELECT DISTINCT [a] FROM [Table_1]"></asp:SqlDataSource>
            <br />
            <br />
            <asp:DropDownList ID="DropDownList2" runat="server"
                DataSourceID="SqlDataSource2" DataTextField="b" DataValueField="b">
            </asp:DropDownList>
            <asp:SqlDataSource ID="SqlDataSource2" runat="server"
                ConnectionString="<%$ ConnectionStrings:DB_firstConnectionString8 %>"
                SelectCommand="SELECT DISTINCT [b] FROM [Table_1]"></asp:SqlDataSource>
            <br />
            <br />
            <asp:DropDownList ID="DropDownList3" runat="server"
                DataSourceID="SqlDataSource3" DataTextField="c" DataValueField="c">
            </asp:DropDownList>
            <asp:SqlDataSource ID="SqlDataSource3" runat="server"
                ConnectionString="<%$ ConnectionStrings:DB_firstConnectionString9 %>"
                SelectCommand="SELECT DISTINCT [c] FROM [Table_1]"></asp:SqlDataSource>
            <br />
            <br />
            <br />
            <asp:DropDownList ID="DropDownList4" runat="server"
                DataSourceID="SqlDataSource4" DataTextField="d" DataValueField="d">
            </asp:DropDownList>
            <asp:SqlDataSource ID="SqlDataSource4" runat="server"
                ConnectionString="<%$ ConnectionStrings:DB_firstConnectionString10 %>"
                SelectCommand="SELECT DISTINCT [d] FROM [Table_1]"></asp:SqlDataSource>
            <br />
            <br />
            <br />
            <br />
            <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
                DataSourceID="SqlDataSource5">
                <Columns>
                    <asp:BoundField DataField="a" HeaderText="a" SortExpression="a" />
                    <asp:BoundField DataField="b" HeaderText="b" SortExpression="b" />
                    <asp:BoundField DataField="c" HeaderText="c" SortExpression="c" />
                    <asp:BoundField DataField="d" HeaderText="d" SortExpression="d" />
                    <asp:BoundField DataField="e" HeaderText="e" SortExpression="e" />
                    <asp:BoundField DataField="f" HeaderText="f" SortExpression="f" />
                </Columns>
            </asp:GridView>
            <asp:SqlDataSource ID="SqlDataSource5" runat="server"
                ConnectionString="<%$ ConnectionStrings:DB_firstConnectionString11 %>"
                SelectCommand="SELECT [a], [b], [c], [d], [e], [f] FROM [Table_1] WHERE (([a] = @a) AND ([b] = @b) AND ([c] = @c) AND ([d] = @d))">
                <SelectParameters>
                    <asp:ControlParameter ControlID="DropDownList1" Name="a"
                        PropertyName="SelectedValue" Type="String" />
                    <asp:ControlParameter ControlID="DropDownList2" Name="b"
                        PropertyName="SelectedValue" Type="String" />
                    <asp:ControlParameter ControlID="DropDownList3" Name="c"
                        PropertyName="SelectedValue" Type="String" />
                    <asp:ControlParameter ControlID="DropDownList4" Name="d"
                        PropertyName="SelectedValue" Type="String" />
                </SelectParameters>
            </asp:SqlDataSource>
        </form>
    </body>
</html>

我有一个小的SQL表，我希望在从下拉框中选择值时，它应该在该表中显示结果。我无法做到这一点。有什么想法吗？

Answer 1

你的逻辑听起来很合理。

如果您希望在更改每个DropDownList的值后立即反映更改，则需要将AutoPostBack="True"属性添加到 每个 > 即可。举个例子，这就是第一个看起来的样子：

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True"
    DataSourceID="SqlDataSource1" DataTextField="a" DataValueField="a">
</asp:DropDownList>

我能看到的另一件事会导致您的表格无法填写，因为GridView的SQL查询过于严格。也许您打算在OR条款中使用AND而不是WHERE？

编辑：还有一个想法，可能是您的GridView在所有DropDownList被数据绑定之前被数据绑定。这会导致他们还没有SelectedValues，所以当ControlParameter获得数据绑定时，GridView s将没有值。您需要找到一种等待所有DropdownLists数据绑定的方法，然后使用此代码重新绑定GridView：

SqlDataSource5.DataBind(); GridView1.DataBind();

提示：要检查并确保这是您的问题，您可以将该代码放入每个的 _DataBound 事件中你的 DropDownList 。效率不高，但应该有效。

显示表格中下拉框的结果

1 个答案: