How to sort data using query strings

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C#

ASP.NET

In my Default.aspx page I have 2 datalist, first one is populated with categories and second one is populated with colors, ( as item template for both of them im using hyperlink) and I have listview that shows products.

So i want to sort data using those two datalists.... when I select one of categories the listview is populated with that category in the same page for e.g : - Default.aspx?CategoryID=1
( which i have done that)... but when I want this category products to be also sorted by
colors now here is the problem ...!!! I dont know how to achieve that :\

I know that after selecting second datalist whith color, url should be something like this:

Default.aspx?CategoryID=1&Color=red
or
Default.aspx?CategoryID=1&ColorID=1

any idea ?!

HERE IS Code

<div class="Div1" style="width: 150px; float: left;">
    <p>

        <asp:DataList ID="CateoriesDataList" runat="server">
            <HeaderTemplate>
                Categories
            </HeaderTemplate>
            <ItemTemplate>
                <asp:HyperLink ID="CategoryHyperLink" runat="server" Text='<%#Eval("CategoryName").ToString() %>'
                     NavigateUrl='<%#String.Format("Categories.aspx?Category=" + (Eval("CategoryID").ToString() + "&" +Request.QueryString.ToString())) %>'></asp:HyperLink>

            </ItemTemplate>
        </asp:DataList>
    </p>
    <p>
        <asp:DataList ID="ColorsDataList" runat="server">
            <HeaderTemplate>
                Colors
            </HeaderTemplate>
            <ItemTemplate>
                <asp:HyperLink ID="ColorLink" runat="server" Text='<%# Eval("Color").ToString() %>'
                        NavigateUrl='<%#String.Format("Categories.aspx?Category=" + (Eval("CategoryID").ToString() + "&" +Request.QueryString.ToString())) %>'></asp:HyperLink>
            </ItemTemplate>
        </asp:DataList>
    </p>
    </div>
    <div class="Div2" style="float: left; width: 300px;">
        <asp:DataList ID="ProductsDataList" runat="server">
            <HeaderTemplate>
                Products
            </HeaderTemplate>
            <ItemTemplate>
                <asp:Image ID="Image1" runat="server" Height="53px" Width="65px" />
                <asp:HyperLink ID="HyperLink3" runat="server">HyperLink</asp:HyperLink>
                <br />
            </ItemTemplate>
        </asp:DataList>
    </div>

So its something like when you baying shoes from Footlocker.com ... and then you doing some kind of sorting lake: Basketball shoes, price, brand, size... etc
so thats my issue

I like to select category then i like to sort selected data by color or price...and my Default.asx?CategoryID=1&colorID=1 not to show duplicated parameters when again I want to filter by categories exp: Default.asx?CategoryID=3&CategoryID=1&colorID=1

if someone have any idea or can lead me to another source which referes to this kind of issues, I will be very thankful...
I Appreciete your time truely