Try following:
<asp:LinkButton ID="LinkButton1" PostBackUrl='<%# String.Format("ProductCatalog.aspx?ID={0}",Eval("ProductID")) %>' runat="server"><5000</asp:LinkButton>
In addition if your
ProductID
data type is
int
then you need to use the following code:
if(Request.QueryString["ID"]!="" && Request.QueryString["ID"]!=null){
string query = "Select * from Products where ProductID= " +Convert.ToInt32(Request.QueryString["ID"].ToString()) + " AND UnitCost < 5000";
}
UPDATED
*********************************
Assign this property at server side :
LinkButton4.PostBackUrl = "ProductCatalog.aspx?ID=" + ProductID;
OR
Replace
LinkButton
by
HyperLink
as
LinkButtons
were originally designed to do a postback .
<asp:HyperLink ID="HyperLink1" runat="server" NavigateUrl='<%# Eval("ProductID", "ProductCatalog.aspx?ID={0}") %>'></asp:HyperLink>
Let me know your result.