Using TextFieldParser with different fixed lengths - vb.net

Question

I have a system that is generating a text file that contains an unknown amount of data. I have two separate chunks of code one for Payment and one for Distribution. I know I will have at least one Payment and one Distribution (Payment has 23 fields with varying widths and Distribution has 12 fields).
Payment Field lengths are: {10, 1, 10, 8, 1, 20, 13, 1, 8, 8, 8, 40, 40, 40, 40, 40, 25, 2, 9, 40, 10, 20, 6}
Distribution Field lengths are: {10, 1, 10, 20, 40, 13, 1, 40, 40, 10, 1, 14}
The payment field is 400 characters and then the Distribution field is 200 characters. I can have one distribution field or many distribution fields as well as payment fields, but the payment fields do not go in order.
Example of the Payment structure [DO NOT REMOVE SPACES] I need to maintain the structure just in case there is a value there:
00000041285111 20140106EDA0000-001 0000010636317+201401012014010320140106 Some Tax Company Non testing agency service TEST GROUP INC 11#####23
Example of the Distribution structure [DO NOT REMOVE SPACES] I need to maintain the structure just in case there is a value there:
00000041286111 DA0000-005 0000000016731+ 666111 98552
I need to be able to parse through the first Payment gather all of the values in the fixed length, and somehow switch the length of fields to be the distribution fields until I get all of those, and switch it back if it goes back to a Payment.
Here is the code that I have:
Using MyReader As New Microsoft.VisualBasic.FileIO.
TextFieldParser("C:\COM_20140103_173912.txt")
'This field parser gives me the first 400characters with not problems
MyReader.TextFieldType =
Microsoft.VisualBasic.FileIO.FieldType.FixedWidth
MyReader.FieldWidths = {10, 1, 10, 8, 1, 20, 13, 1, 8, 8, 8, 40, 40, 40, 40, 40, 25, 2, 9, 40, 10, 20, 6}
Dim currentRow As String()
While Not MyReader.EndOfData
Try
currentRow = MyReader.ReadFields()
Dim currentField As String
For Each currentField In currentRow
MsgBox(currentField)
Next
Catch ex As Microsoft.VisualBasic.FileIO.MalformedLineException
MsgBox("Line " & ex.Message &
"is not valid and will be skipped.")
End Try
End While
End Using
I got this code from http://msdn.microsoft.com/en-us/library/microsoft.visualbasic.fileio.textfieldparser.fieldwidths.aspx
I have done research and I can't figure out how to manipulate this to do what I need it to do. Any help would be appreciated. I hope I gave enough information, and if you need me to explain it differently I can.
Thanks,
John

Answer 1

Here's one idea. The TextFielParser constructor can also take a stream as its parameter. Use a regular StreamReader to read the file line by line and then use a StringReader with the TextFieldParser to process each line based on it's length. Something like the following (untested):
Imports Microsoft.VisualBasic.FileIO
Imports System.IO
Sub Main
Using rdr As New StreamReader("C:\COM_20140103_173912.txt")
Dim currentLine As String = rdr.ReadLine()
While currrentLine IsNot Nothing
Dim currentRow As String()
If currentLine.Length = 400 Then
currentRow = processDistributionRow(currentLine)
Else
currentRow = processPaymentRow(currentLine)
End If
If currentRow IsNot Nothing Then
'Process current set of fields
End If
currentLine = rdr.ReadLine()
End While
End Using
End Sub
'This method uses a TextFieldParser to process a single line of a file that is passed in
Private Function processDistributionRow(currentLine As String)
Dim result As String()
Using strStream As New StringStream(currentLine)
Using MyReader As New TextFieldParser(strStream)
MyReader.TextFieldType = FieldType.FixedWidth
MyReader.FieldWidths = {10, 1, 10, 8, 1, 20, 13, 1, 8, 8, 8, 40, 40, 40, 40, 40, 25, 2, 9, 40, 10, 20, 6}
Try
result = MyReader.ReadFields()
Dim currentField As String
Catch ex As Microsoft.VisualBasic.FileIO.MalformedLineException
MsgBox("Line " & ex.Message & "is not valid and will be skipped.")
End Try
End Using
End Using
return result
End Function
'This method uses a TextFieldParser to process a single line of a file that is passed in
Private Function processPaymentRow(currentLine As String)
Dim result As String()
Using strStream As New StringStream(currentLine)
Using MyReader As New TextFieldParser(strStream)
MyReader.TextFieldType = FieldType.FixedWidth
MyReader.FieldWidths = {?, ?, ?} 'Set proper field widths for the payment row here
Try
result = MyReader.ReadFields()
Dim currentField As String
Catch ex As Microsoft.VisualBasic.FileIO.MalformedLineException
MsgBox("Line " & ex.Message & "is not valid and will be skipped.")
End Try
End Using
End Using
return result
End Function
' Define other methods and classes here