My.Computer.FileSystem.OpenTextFieldParser Method 

The OpenTextFieldParser method allows you to create a TextFieldParser Object, which provides a way to easily and efficiently parse structured text files, such as logs. The TextFieldParser object can be used to read both delimited and fixed-width files.

' Usage
Dim value As TextFieldParser = My.Computer.FileSystem.OpenTextFieldParser(file)
Dim value As TextFieldParser = My.Computer.FileSystem.OpenTextFieldParser(file ,delimiters)
Dim value As TextFieldParser = My.Computer.FileSystem.OpenTextFieldParser(file ,fieldWidths)
' Declaration
Public Function OpenTextFieldParser( _
   ByVal file As String _
) As TextFieldParser
' -or-
Public Function OpenTextFieldParser( _
   ByVal file As String, _
   ByVal delimiters As String() _
) As TextFieldParser
' -or-
Public Function OpenTextFieldParser( _
   ByVal file As String, _
   ByVal fieldWidths As Integer() _
) As TextFieldParser

Parameters

• file
  String. The file to be opened with the TextFieldParser. Required.

• delimiters
  String(). Delimiters for the fields. Required.

• fieldWidths
  Integer(). Widths of the fields. Required.

Return Value

TextFieldParser

Exceptions

The following conditions may cause an exception:

• The path is not valid for one of the following reasons: it is a zero-length string; it contains only white space; it contains invalid characters; or it is a device path (starts with \\.\) (ArgumentException).

• The file name ends with a trailing slash (ArgumentException).

• The path is not valid because it is Nothing (ArgumentNullException).

• Specified file does not exist (FileNotFoundException).

• Specified file is in use (IOException).

• The path exceeds the system-defined maximum length (PathTooLongException).

• A file or directory name in the path contains a colon (:) or is in an invalid format (NotSupportedException).

• The user lacks necessary permissions to view the path (SecurityException).

• A row cannot be parsed using the specified format (MalformedLineException). The exception message specifies the line causing the exception, while the TextFieldParser.ErrorLine Property is assigned the text contained in the line.

• The user does not have sufficient permissions to access the file (UnauthorizedAccessException).

Tasks

The following table lists examples of tasks involving the My.Computer.FileSystem.OpenTextFieldParser method.

Example

This example opens the TextFieldParser reader and uses it to read from C:\TestFolder1\Test1.txt.

Dim reader As Microsoft.VisualBasic.FileIO.TextFieldParser
reader = My.Computer.FileSystem.OpenTextFieldParser _
("C:\TestFolder1\test1.txt")
reader.TextFieldType = Microsoft.VisualBasic.FileIO.FieldType.Delimited
reader.delimiters = New String() {","}
Dim currentRow As String()
While Not reader.EndOfData
   Try
       currentRow = reader.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

Requirements

Namespace: Microsoft.VisualBasic.MyServices

Class: FileSystemProxy (provides access to FileSystem)

Assembly: Visual Basic Runtime Library (in Microsoft.VisualBasic.dll)

Availability by Project Type

Permissions

The following permissions may be necessary:

For more information, see Code Access Security and Requesting Permissions.

See Also

Tasks

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

Reference

My.Computer.FileSystem Object
TextFieldParser Object
OpenTextFieldParser

Concepts

Parsing Text Files with the TextFieldParser Object

Other Resources

Reading from Files in Visual Basic