如何将 sqldatasource 默认值设置为数据库字段值。我有一个像这样的编码,
<asp:DropDownList ID="ddVehicle" runat="server" AppendDataBoundItems="true" CssClass="drop" DataSourceID="SqlDataSource4" DataTextField="VehicleType" DataValueField="VehicleId">
<asp:ListItem Value="">-Select-</asp:ListItem>
</asp:DropDownList>
<asp:SqlDataSource ID="SqlDataSource4" runat="server" ConnectionString="<%$ ConnectionStrings:TAXIConnectionString %>" SelectCommand="SELECT [VehicleId], [VehicleType] FROM [VehicleMaster] WHERE ([VehicleId] = @Vehicle or [Status] = @Status1)">
<SelectParameters>
<asp:Parameter DefaultValue="???" Name="Vehicle" Type="String" />
<asp:Parameter DefaultValue="Available" Name="Status1" Type="String" />
</SelectParameters>
</asp:SqlDataSource>
帮我。