將多個默認值設置爲SqlDataSource Where條件

Question

我有一個從SqlDataSource填充的列表視圖。它根據查詢字符串中的類別值顯示數據庫中的產品列表。我在產品表中的類別是New|Fiction|Auto|Text。我如何設置默認值來顯示所有類別。從DropdownList中選擇類別。當我在下拉列表中選擇ALL時，我需要顯示所有產品。

DROPDOWNLIST

<asp:DropDownList runat="server" id="ddl" OnSelectedIndexChanged="SelectionChanged" AutoPostBack="true"> 
     <asp:ListItem Text="All" ></asp:ListItem> 
     <asp:ListItem Text="Fiction" Value="~/Bio.aspx?Category=Fiction" /> 
     <asp:ListItem Text="TextBooks" Value="~/Bio.aspx?Category=Text" /> 
     <asp:ListItem Text="Biography" Value="~/Bio.aspx?Category=Auto" /> 
     <asp:ListItem Text="New Release" Value="~/Bio.aspx?Category=New" /> 
    </asp:DropDownList> 


<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:2016_675_z1787626ConnectionString %>" SelectCommand="SELECT * FROM [Bio] WHERE ([Category] = @Category)" > 
     <SelectParameters> 
      <asp:QueryStringParameter Name="Category" QueryStringField="Category" Type="String" /> 
     </SelectParameters> 
</asp:SqlDataSource> 

Answer 1

您將需要修改其中的SELECT語句子句。

<asp:DropDownList runat="server" id="ddl" 
    OnSelectedIndexChanged="SelectionChanged" 
    AutoPostBack="true"> 
    <asp:ListItem Text="All" Value="~/Bio.aspx?Category=ALL" ></asp:ListItem> 
    ... 
</asp:DropDownList> 

SELECT * FROM [Bio] WHERE (@Category = '' OR @Category = 'ALL' OR [Category] = @Category)