How to add two list of custom class type to one list. And bind to GridView

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C#

LINQ

I am trying to add two list to one list. i am using linq to populate the list but it is showing some error. And i have to bind the new list contain two other list to grid view.

The follwoing is my code and it is working fine

DataTable table;
        protected void Page_Load(object sender, EventArgs e)
        {
            bind();
        }
        public void bind()
        {
            SqlConnection conn = new SqlConnection(@"Data Source=CLAYSYSCH0028\Sharepoint;Initial Catalog=ShankarMS;Integrated Security=True");
            conn.Open();
            SqlCommand comm = new SqlCommand();
            comm.CommandText = "select * from UserDetails";
            comm.Connection = conn;
            SqlDataAdapter adapter = new SqlDataAdapter(comm);
            DataSet set = new DataSet();
            adapter.Fill(set);
            table = set.Tables[0];
            //Stack<support> stack = new Stack<support>();
            List<int> first = new List<int>((from x in table.AsEnumerable() where x.Field<int>("ID") != 177 select x.Field<int>("ID")).ToArray());
            List<int> second = new List<int>((from x in table.AsEnumerable() where x.Field<int>("ID") == 180 select x.Field<int>("ID")).ToArray());
            List<int> main = new List<int>();
            if (second.Count > 0)
            {
                main.InsertRange(0, second);
                main.InsertRange(1, first);
            }
            else
            {
                main.InsertRange(0, first);
            }

            //stack.AddRange((from x in table.AsEnumerable() where x.Field<int>("ID") != 177 select x.Field<int>("ID")).ToList());
            grid.DataSource = main;
            grid.DataBind();
        }

This is my grid

<asp:GridView ID="grid" runat="server" ClientIDMode="Inherit" >
        </asp:GridView>

But my requirment is i have to declare the first and second list as a custom class type.
My

custom class is

public class support
   {
       public int id
       {
           get;
           set;
       }
       public string Name
       {
           get;
           set;
       }
   }

And i have to bind the new list main to grid. And i have to bind the values to template field in grid view.

And that grid is like this

<asp:GridView ID="lst" runat="server" ClientIDMode="Inherit">
            <Columns>
                <asp:TemplateField>
                    <ItemTemplate>
                        <asp:Label ID="lbl" runat="server" Text='<%# Eval("ID") %>'></asp:Label>
                        <asp:Label ID="Label1" runat="server" Text='<%# Eval("FirstName") %>'></asp:Label>
                    </ItemTemplate>
                </asp:TemplateField>
            </Columns>
        </asp:GridView>

Please help me.