Here is a solution using few
if..else.. and
StringBuilder -
Replace this section
DataTable dt = this.GetData("select [Name], [Latitude], [Longitude] from [MAIN AREA]");
rptMarkers.DataSource = dt;
rptMarkers.DataBind();
with following-
StringBuilder query=new StringBuilder("select [Name], [Latitude], [Longitude] from [MAIN AREA] where 1=1");
if(DropDownList1.SelectedIndex>0)
{
query.Append(" and [Name]="+DropDownList1.SelectedValue.ToString());
}
if(DropDownList2.SelectedIndex>0)
{
query.Append(" and [Latitude]="+DropDownList2.SelectedValue.ToString());
}
if(DropDownList3.SelectedIndex>0)
{
query.Append(" and [Longitude]="+DropDownList3.SelectedValue.ToString());
}
DataTable dt = this.GetData(query);
rptMarkers.DataSource = dt;
rptMarkers.DataBind();
Hope, it helps !
If I have missed something, please let me know :)