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How to: Read From Comma-Delimited Text Files in Visual Basic 

The TextFieldParser object provides a way to easily and efficiently parse structured text files, such as logs. The TextFieldType property defines whether it is a delimited file or one with fixed-width fields of text.

To parse a comma delimited text file

  1. Create a new TextFieldParser. The following code creates the TextFieldParser named MyReader and opens the file test.txt.

    Using MyReader As New _
    Microsoft.VisualBasic.FileIO.TextFieldParser _
    ("C:\TestFolder\test.txt")
    
    
  2. Define the TextField type and delimiter. The following code defines the TextFieldType property as Delimited and the delimiter as ",".

    MyReader.TextFieldType = FileIO.FieldType.Delimited
    MyReader.SetDelimiters(",")
    
    
  3. Loop through the fields in the file. If any lines are corrupt, report an error and continue parsing. The following code loops through the file, displaying each field in turn and reporting any fields that are formatted incorrectly.

    
    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
    
    
  4. Close the While and Using blocks with End While and End Using.

       End While
    End Using
    
    

Example

This example reads from the file test.txt.

Using MyReader As New _
Microsoft.VisualBasic.FileIO.TextFieldParser("C:\testfile.txt")
   MyReader.TextFieldType = FileIO.FieldType.Delimited
   MyReader.SetDelimiters(",")
   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

Robust Programming

The following conditions may cause an exception:

See Also

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