An item with the same key has already been added.

An item with the same key has already been added.

i am using zoho analytics for fetching data. I have used sql queries for fetching data. I have 45 tables and I have used for loop for getting data from all tables. I can get data for the first iteration. For the second iteration I am getting error as,
An item with the same key has already been added.

I am getting error for the statement. It executes when intI is 0. It gives error for intI=1.

RepClient.ExportDataUsingSQL(tableURI, "JSON", strFile, strQry, config)

The code is as follows ,
  2. Dim objDT As New DataTable
  3.         Dim objDS As New DataSet
  4.         Dim intI As Integer
  5.         Dim strTable As String

  7.  ZCRMRestClient.Initialize(config)
  8.             Dim client As ZohoOAuthClient = ZohoOAuthClient.GetInstance()
  9.             Dim grantToken As String 
  10.             Dim tokens As ZohoOAuthTokens
  11.             Dim accessToken As String = tokens.AccessToken
  12.             Dim refreshToken As String = tokens.RefreshToken
  13.             Dim RepClient As IReportClient
  14.             Dim tableURI As String 
  15.             Dim strFile As String
  16.             Dim strOP As String
  17.             Dim jsonString


  20.             For intI = 0 To objDTTable.Rows.Count - 1
  21.                 strFile = "d:\\Data.json"
  22.                 'strQry = "select * from Customer WHERE ""Customer Name""='AKSHAR DEVELOPERS'"
  23.                 File.Delete(strFile)

  25.                 strTable = objDTTable.Rows(intI).Item("Analytics_Table_Name")
  26.                 strQry = "select * from " & strTable
  27.                 RepClient.ExportDataUsingSQL(tableURI, "JSON", strFile, strQry, config)


  30.                 strOP = JsonConvert.SerializeObject(strFile, Formatting.Indented)
  31.                 jsonString = File.ReadAllText(strFile)

  33.                 objDT = Tabulate(jsonString)
  34.                 'ExportToExcel("d:\1.xls", objDT)
  35.                 CopyData(objDT, strTable)

  37.                 'Threading.Thread.Sleep(360001)
  38.                 client = Nothing
  39.                 grantToken = Nothing
  40.                 tokens = Nothing
  41.                 accessToken = Nothing
  42.                 refreshToken = Nothing
  43.                 RepClient = Nothing
  44.                 tableURI = Nothing
  45.             Next
  46.             Return objDT