convert table to json

Question

static public string table2Json(DataSet ds, int table_no)
       {
           try
           {
               // Given a Dataset & Table NO , function returns a 2 dim JSON Array of values in that table
               int rcnt = ds.Tables[table_no].Rows.Count; // Row Count
               int ccnt = ds.Tables[table_no].Columns.Count; // Col Count


               object[][] tb = new object[rcnt][];

               int r = 0;
               foreach (DataRow dr in ds.Tables[table_no].Rows)
               {
                   tb[r] = new object[ccnt];
                   for (int col = 0; col < ccnt; col++)
                   {
                       tb[r][col] = dr[col];

                       if ((tb[r][col]).Equals(System.DBNull.Value))
                           tb[r][col] = "";
                   }
                   r++;
               }

               var table= JsonConvert.SerializeObject(tb);
               return table;
           }

I have some code for convert table to json string i want to remove  for loo from these code how does it is possible