public DataTable GetTables()
    {
        DataSet ds = new DataSet();
        string sql = "SELECT TABLE_CATALOG,TABLE_SCHEMA, TABLE_NAME,TABLE_TYPE FROM INFORMATION_SCHEMA.TABLES";
        using (SqlConnection conn = new SqlConnection(ConnectionString))
        {
            if (conn.State == ConnectionState.Closed) conn.Open();
            SqlDataAdapter sda = new SqlDataAdapter(sql, conn);
            sda.Fill(ds);
        }
        return ds != null && ds.Tables.Count > 0 ? ds.Tables[0] : null;
     }