处理日期时的错误处理

Question

代码从服务器下载CSV文件，然后清理并输出必要的数据到另一个CSV文件。

我的问题是，在星期日和节假日没有在服务器上创建的文件。因此，当From和To date之间遇到这样的日期时，程序将停止进一步。这怎么可以避免？

如果前一天没有文件，我希望程序转到下一个日期。

Private Declare Function URLDownloadToFile Lib "urlmon" _ 
Alias "URLDownloadToFileA" _ 
(ByVal pCaller As Long, _ 
ByVal szURL As String, _ 
ByVal szFileName As String, _ 
ByVal dwReserved As Long, _ 
ByVal lpfnCB As Long) As Long 

Private Declare Function DeleteUrlCacheEntry Lib "Wininet.dll" _ 
Alias "DeleteUrlCacheEntryA" _ 
(ByVal lpszUrlName As String) As Long 

Private Const ERROR_SUCCESS As Long = 0 
Private Const BINDF_GETNEWESTVERSION As Long = &H10 
Private Const INTERNET_FLAG_RELOAD As Long = &H80000000 

Private Sub Command1_Click() 
On Error GoTo Err 
Const q As String = "-" 
Dim tmp As String, fName As String, Pos As Long, fPath As String 
Dim first As Date, last As Date, spath As String, d As Date 
Dim sLineIn As String 
Dim sLineOut As String 
Dim sCols() As String 
Dim sSymbol As String 
Dim sName As String 
Dim sDate As String 
Dim sOpen As String 
Dim sHigh As String 
Dim sLow As String 
Dim sClose As String 
Dim sVolume As String 
Dim sOpenIntrest As String 
Dim sLastSymbol As String 
Dim nCounter As String 

cap = Me.Caption 
If Dir(App.Path & "\NCDEX\", vbDirectory) = "" Then 
MkDir App.Path & "\NCDEX\" 
End If 
spath = App.Path & "\NCDEX\" ' folder to save files : note trailing \ 
first = MonthView1 
last = MonthView2 
strURL = "http://www.ncdex.com/Downloads/Bhavcopy_Summary_File/Export_csv/" 
For d = first To last 
sSourceURL = strURL & Format(d, "MM") & q & Format(d, "dd") & q & Format(d, "yyyy") & ".csv" 
Debug.Print sSourceURL 
fName = Format(d, "dd-mm-yyyy") & ".csv" 
Debug.Print fName 
slocalfile = spath & fName 
Me.Caption = "Downloading " & fName 
Call DeleteUrlCacheEntry(sSourceURL) 
URLDownloadToFile 0&, sSourceURL, slocalfile, BINDF_GETNEWESTVERSION, 0& 

' sLastSymbol = "zzz" 'Set to something Symbol cannot possibly be initially. 
nCounter = 0 
Open App.Path & "\temp.csv" For Output As #2 
Open App.Path & "\NCDEX\" & fName For Input As #1 
Do While Not EOF(1) 
Line Input #1, sLineIn 
sLineIn = Replace(sLineIn, Chr(39), vbNullString) 
     sLineIn = Replace(sLineIn, Chr(34), vbNullString) 
     sLineIn = Replace(sLineIn, " ", vbNullString) 
     sCols = Split(sLineIn, ",") 
     sSymbol = sCols(0) 
     sDate = sCols(15) 
     sOpen = sCols(6) 
     sHigh = sCols(7) 
     sLow = sCols(8) 
     sClose = sCols(9) 
     sVolume = sCols(10) 
     sOpenIntrest = sCols(14) 

     If sSymbol = sLastSymbol Then 
     nCounter = nCounter + 1 
     Else 
     nCounter = 1 
     End If 
     sLastSymbol = sSymbol 

     Debug.Print sLineIn 
     If sCols(10) <> "0" Then 
    ' Only write lines that do not have "0" in Cols(12) 

     sLineOut = sSymbol & "_" & nCounter & "," & sDate & "," & sOpen & "," & sHigh & "," & sLow & "," & sClose & "," & sVolume & "," & sOpenIntrest 
     Print #2, sLineOut 
     End If 
    Loop 
    Close #1 
    Close #2 

    ' Delete file 1 and rename file 2 as the original file 1 name. 
    ' // Delete the original file 
    Kill slocalfile 
    ' // Rename the temp file to the original name 
    Name App.Path & "\temp.csv" As slocalfile 

Next 
Me.Caption = cap 
'YOU CAN TAKE THIS BELOW OUT IF U DONT WANT IT 
MsgBox "Saved to " & spath, vbInformation + vbOKOnly, "Success!" 
Exit Sub 
Err:  MsgBox "Error", vbCritical + vbOKOnly, "Market Was Closed" 
End Sub 

Answer 1

你不看URLDownloadToFile（）的返回值。如果文件已经开始下载，则返回S_OK（= 0）。如果“指定资源或回调接口无效”。那么它返回INET_E_DOWNLOAD_FAILURE。

所以，你应该做的：

If URLDownloadToFile(0&, sSourceURL, slocalfile, BINDF_GETNEWESTVERSION, 0&) = S_OK Then 

    ' sLastSymbol = "zzz" 'Set to something Symbol cannot possibly be initially. 
    nCounter = 0 
    Open App.Path & "\temp.csv" For Output As #2 
    Open App.Path & "\NCDEX\" & fName For Input As #1 
    Do While Not EOF(1) 
     Line Input #1, sLineIn 
     sLineIn = Replace(sLineIn, Chr(39), vbNullString) 
     sLineIn = Replace(sLineIn, Chr(34), vbNullString) 
     sLineIn = Replace(sLineIn, " ", vbNullString) 
     sCols = Split(sLineIn, ",") 
     sSymbol = sCols(0) 
     sDate = sCols(15) 
     sOpen = sCols(6) 
     sHigh = sCols(7) 
     sLow = sCols(8) 
     sClose = sCols(9) 
     sVolume = sCols(10) 
     sOpenIntrest = sCols(14) 

     If sSymbol = sLastSymbol Then 
      nCounter = nCounter + 1 
     Else 
      nCounter = 1 
     End If 

     sLastSymbol = sSymbol 

     Debug.Print sLineIn 
     If sCols(10) <> "0" Then 
      ' Only write lines that do not have "0" in Cols(12) 
      sLineOut = sSymbol & "_" & nCounter & "," & sDate & "," & sOpen & "," & sHigh & "," & sLow & "," & sClose & "," & sVolume & "," & sOpenIntrest 
      Print #2, sLineOut 
     End If 
    Loop 
    Close #1 
    Close #2 

    ' Delete file 1 and rename file 2 as the original file 1 name. 
    ' // Delete the original file 
    Kill slocalfile 
    ' // Rename the temp file to the original name 
    Name App.Path & "\temp.csv" As slocalfile 
End If 

我还要提到的是在看文档，它似乎在暗示，这个函数返回的文件开始下载。这可能是因为你的文件很小，它在函数返回之前下载了整个文件。但是，如果您的文件变得足够大，则可能仍会在您自己的代码正在执行时下载，这意味着文件访问会失败，或者更糟糕的是会破坏您的数据。

查看MSDN文档中的备注部分。