parse several field using file helper

问题

Good day to all,

i have a problem regarding CSV parse using File Helper. My CSV is look like this

,,,026642,0,00336,05,19,"WATERMELON *",19,"1 ",,,,,,,,0,,001.99.,0,,,,,0,,0,0,,,,,,,,,,,,,,,,,,51,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,026645,0,00338,05,19,"ONION ",19,"*1 ",,,,,,,,0,,002.99.,0,,,,,0,,0,0,,,,,,,,,,,,,,,,,,51,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,026687,0,00380,05,19,"MUSHROOM ",19," (BLACK FUNGUS) ",,,,,,,,0,,021.90.,0,,,,,0,,0,0,,,,,,,,,,,,,,,,,,51,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

which this CSV have 116 column / field.

The problem was i just need only 4 field from whole line which

Field 4 = 026687, Field 9 = "WATERMELON *", Field 11 = "(BLACK FUNGUS)", Field 21 = 002.99.

When i using wizard which a very good solution to make instance class, and i put FieldValueDiscarded _ on top of every other fields i don't need it, it just print a same as CSV input.

Please give me some advise how do i extract only needed field to write into output.

Thank you

UPDATED : After research some more, i finally getting clear about this error. This error happen because class non-inherited so i cannot get specific field into another class. By declare mapping class as inherited class, i can get specific field.

However, i stuck at how to retrieve functions inside the class who inherited from mapping class. This is my code `Imports System.Text Imports System.IO Imports FileHelpers

Public Class ProcessField : Inherits InputCSV

Public Function MyPLUc(ByVal value As Integer)
    Dim PLUc As String
    MyBase.PLU = value
    PLUc = (0 + 0 + value)
    Return (0 + 0 + value)
End Function
Public Function MyStatusc(ByVal value As Integer)
    MyBase.Status = value
    Dim Status As Integer
    If value > 0 Then
        Status = 800
    Else
        Status = 900
    End If
    Return (0 + Status)
End Function
Public Function MyUnitPricec(ByVal value As Integer)
    MyBase.UnitPrice = value
    Dim UP As Integer
    UP = value
    Dim bytes As Byte() = System.Text.Encoding.Unicode.GetBytes(UP)
    Return (0 + 0 + 0 + UP)
End Function
Public Function MyLabelFormat(ByVal value As Integer)
    Return (1 + 1)
End Function
Public Function MyEAN(ByVal value As Integer)
    Return (0 + 6)
End Function
Public Function MyCName(ByVal value As String)
    MyBase.CName1 = value
    Dim hexString As String = Hex(value)
    Return (hexString)
End Function
Public Function MyBCC(ByVal value As String)
    value = (0 + 0)
    Return (0 + 0)

End Function

End Class`

and the problem is how i retrieve all return value in these function

回答1:

I'm not sure I understand your question, but I think you are making things more complicated than you need.

You can just create your FileHelpers class with 116 string fields. They should be (public) fields, NOT properties. You should NOT subclass the FileHelpers class. Do not try to use the FileHelpers class as a normal class (i.e., with properties, functions, etc, subclasses). Think of the FileHelpers class as a 'specification' of your CSV format only.

To import, you write something like:

Dim engine As New FileHelperEngine(GetType(RecordSpec)) 

' To Read Use: 
Dim results As RecordSpec() = DirectCast(engine.ReadFile("FileIn.txt"), RecordSpec())

Then you have an array of RecordSpec. Each RecordSpec will have all 116 fields populated, but just ignore the fields you don't need. Then loop through the results and do whatever you want with the values. For instance, perhaps you need to map the imported fields to another (more normal) MyProduct class with properties instead of fields and perhaps with additional logic.

For Each recordSpec As RecordSpec In results
  Dim myProduct = New MyProduct()
  myProduct.Id = recordSpec.Field4
  myProduct.Name = recordSpec.Field9
  myProduct.Category = recordSpec.Field23
  ' etc.
Next

In summary: the RecordSpec class should only be used to define the structure of the CSV file. You use it to populate a simple array with all the values from the file. You then map the values to a more useful class MyProduct.

来源：https://stackoverflow.com/questions/12854253/parse-several-field-using-file-helper

标签

vb.net

filehelpers