My.Computer.FileSystem.OpenTextFieldParser Method

OpenTextFieldParser Method (My.Comp...

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Microsoft Visual Studio 2008/.NET Framework 3.5

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Visual Basic Language Reference

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.

To	See
Read from a delimited text file	How to: Read From Comma-Delimited Text Files in Visual Basic
Read from a fixed-width text file	How to: Read From Fixed-width Text Files in Visual Basic
Read from a text file with multiple formats	How to: Read From Text Files with Multiple Formats in Visual Basic

Example

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

Visual Basic

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

Project type	Available
Windows Application	Yes
Class Library	Yes
Console Application	Yes
Windows Control Library	Yes
Web Control Library	Yes
Windows Service	Yes
Web Site	Yes

Permissions

The following permissions may be necessary:

Permission	Description
FileIOPermission	Controls the ability to access files and folders. Associated enumeration: Unrestricted.
SecurityPermission	Describes a set of security permissions applied to code. Associated enumeration: ControlEvidence.

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

Availability by Project Type

Tasks

Concepts

Reference

Other Resources