Drop down list

Hi could someone please advise me on the following I'm new. I have  adrop down list which I use to sort data from my gridview table. I would like to only display unique items in my dropdown list and not duplicates. Also, I would like to see my whole table in gridview when I open the page and let the user filter it as they like. However, at the moment I don't see the whole table when I open the page, only the drop down list. Here is my code: Please help :)

<%@ Page Title="BikeList" Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="BikeList.aspx.cs" Inherits="Pages_BikeList" %>

<asp:Content ID="Content2" ContentPlaceHolderID="head" Runat="Server">
</asp:Content>
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
    <h1><a id="top">View Our Range</a></h1>
         <p>Below is a complete list of our bikes. Use the drop down box to filter down box to filter the list by manufacturer.</p>
    Manufacturer:
        <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" 
            DataSourceID="SqlDataSource1" DataTextField="Make" DataValueField="Make" AppendDataBoundItems="true">
            <asp:ListItem Value="">Make a Selection</asp:ListItem>
        </asp:DropDownList>
        <asp:SqlDataSource ID="SqlDataSource1" runat="server"
            ConnectionString="<%$ ConnectionStrings:ConnectionString %>" 
            ProviderName="<%$ ConnectionStrings:ConnectionString.ProviderName %>" 
            SelectCommand="SELECT  DISTINCT [Make], [BikeID] FROM [Bike] ORDER BY [BikeID]">
        </asp:SqlDataSource>  
        <asp:GridView ID="GridView1" runat="server" AllowSorting="True" 
            AutoGenerateColumns="False" DataKeyNames="BikeID" DataSourceID="SqlDataSource2" 
            HorizontalAlign="Center" EnableSortingAndPagingCallbacks="True">
            <Columns>
                <asp:BoundField DataField="BikeID" HeaderText="BikeID" InsertVisible="False" 
                    ReadOnly="True" SortExpression="BikeID" />
                <asp:BoundField DataField="Make" HeaderText="Make" SortExpression="Make" />
                <asp:BoundField DataField="Model" HeaderText="Model" SortExpression="Model" />
                <asp:BoundField DataField="Year" HeaderText="Year" SortExpression="Year" ItemStyle-CssClass="textalignright" />
                <asp:BoundField DataField="Capacity" HeaderText="Capacity" ItemStyle-CssClass="textalignright"
                    SortExpression="Capacity" />
                <asp:BoundField DataField="SalePrice" DataFormatString="{0:C}" ItemStyle-CssClass="textalignright"
                    HeaderText="SalePrice" SortExpression="SalePrice" />
                <asp:BoundField DataField="DealerPrice" DataFormatString="{0:C}" ItemStyle-CssClass="textalignright"
                    HeaderText="DealerPrice" SortExpression="DealerPrice" />
                <asp:CheckBoxField DataField="Featured" HeaderText="Featured" 
                    SortExpression="Featured" />
                <asp:ImageField DataImageUrlField="Thumbnail" 
                    DataImageUrlFormatString="~\Images\{0}" HeaderText="Thumbnail">
                </asp:ImageField>
                <asp:HyperLinkField DataNavigateUrlFields="Image" 
                    DataNavigateUrlFormatString="~\Images\{0}" HeaderText="Image" 
                    Text="Larger Image" />
            </Columns>
        </asp:GridView>
        <asp:SqlDataSource ID="SqlDataSource2" runat="server" 
            ConnectionString="<%$ ConnectionStrings:ConnectionString %>" 
            ProviderName="<%$ ConnectionStrings:ConnectionString.ProviderName %>" 
            SelectCommand="SELECT * FROM [Bike] WHERE ([Make] = @Make)">
            <SelectParameters>
                <asp:ControlParameter ControlID="DropDownList1" Name="Make" 
                    PropertyName="SelectedValue" Type="String" />
            </SelectParameters>
        </asp:SqlDataSource>
      
  
</asp:Content>

Are you sure your datasource is bringing sufficient data to fill the GridView?