public  delegate DataTable loadDataTable();

DataTable shops = (cmbShop.Text == "All Shops") ?
      new loadDataTable(() =>
       {
       Program.con.GET_Table_From_DataBase("sh", "select * from shops ");
       return Program.con.dst.Tables["sh"];
       }
      ).Invoke()
     :
       new loadDataTable(() =>
       {
        Program.con.GET_Table_From_DataBase("sh", "select * from shops where shopname='" +  cmbShop.Text + "' ");
        return Program.con.dst.Tables["sh"];
       }
  ).Invoke();

if (cmbShop.Text == "All Shops")
    Program.con.GET_Table_From_DataBase("sh", "select * from shops ");
else
    Program.con.GET_Table_From_DataBase("sh", "select * from shops where shopname='" +  cmbShop.Text + "' ");

DataTable shops = Program.con.dst.Tables["sh"];

Program.con.GET_Table_FromDataBase("sh", string.Format("select * from shops{0}",
                 (cmbShop.Text == "All Shops") ? string.Empty : string.Format(" where shopname='"+cmbShop.Text+"'"));