Join records of multiple DataTables using LINQ in C# .Net

Hi Prasunjeet,

I have created one sample that full-fill your requirement.

HTML

<asp:GridView runat="server" ID="gvDetails">
</asp:GridView>

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        //Hotel Datatable
        DataTable hotel = new DataTable();
        hotel.Columns.AddRange(new DataColumn[2] { 
        new DataColumn("hotelid", typeof(int)), 
        new DataColumn("hotelname", typeof(string)) });
        hotel.Rows.Add(1, "Surya");
        hotel.Rows.Add(2, "Saffron");
        hotel.Rows.Add(3, "Taj");

        //Roomtype Datatable
        DataTable roomtype = new DataTable();
        roomtype.Columns.AddRange(new DataColumn[3] { 
        new DataColumn("roomtypeid", typeof(int)), 
        new DataColumn("roomtypename", typeof(string)), 
        new DataColumn("hotel_id", typeof(int)) });
        roomtype.Rows.Add(1, "Normal AC", 1);
        roomtype.Rows.Add(2, "Normal NonAC", 1);
        roomtype.Rows.Add(3, "Flooring", 2);
        roomtype.Rows.Add(4, "Marble", 2);
        roomtype.Rows.Add(5, "AC Marble", 3);
        roomtype.Rows.Add(6, "NonAC Marble", 3);

        //Room Datatable
        DataTable room = new DataTable();
        room.Columns.AddRange(new DataColumn[3] { 
        new DataColumn("roomid", typeof(int)), 
        new DataColumn("roomno", typeof(string)),
        new DataColumn("roomtype_id", typeof(int)) });
        room.Rows.Add(1, "100", 1);
        room.Rows.Add(2, "101", 2);
        room.Rows.Add(3, "102", 4);
        room.Rows.Add(4, "103", 6);

        //Query
        var result = from htl in hotel.AsEnumerable()
                        join rtype in roomtype.AsEnumerable() on htl.Field<int>("hotelid") equals rtype.Field<int>("hotel_id")
                        join rm in room.AsEnumerable() on rtype.Field<int>("roomtypeid") equals rm.Field<int>("roomtype_id")
                        select new
                        {
                            roomno = rm.Field<string>("roomno"),
                            roomtypename = rtype.Field<string>("roomtypename"),
                            hotelname = htl.Field<string>("hotelname")
                        };
        this.gvDetails.DataSource = result;
        this.gvDetails.DataBind();
    }
}

Screenshot