TextFieldParser Object

The following condition may cause an exception:

• A text field does not match the specified format. For example, in a fixed-width file, one of the fields does not match the specified width. (MalformedLineException).

The TextFieldParser object provides methods and properties for parsing structured text files. Parsing a text file with the TextFieldParser is similar to iterating over a text file, while the ReadFields method to extract fields of text is similar to splitting the strings.

The TextFieldParser can parse two types of files: delimited or fixed-width. Some properties, such as Delimiters and HasFieldsEnclosedInQuotes are meaningful only when working with delimited files, while the FieldWidths property is meaningful only when working with fixed-width files.

The following table lists examples of tasks involving the Microsoft.VisualBasic.FileIO.TextFieldParser object.

This example parses through a tab-delimited text file, Bigfile.

Using MyReader As New Microsoft.VisualBasic.FileIO.TextFieldParser _
("c:\logs\bigfile")
    MyReader.TextFieldType = Microsoft.VisualBasic.FileIO.FieldType.Delimited
    MyReader.Delimiters = New String() {vbTab}
    Dim currentRow As String()
    'Loop through all of the fields in the file. 
    'If any lines are corrupt, report an error and continue parsing. 
    While Not MyReader.EndOfData
        Try
            currentRow = MyReader.ReadFields()
            ' Include code here to handle the row.
        Catch ex As Microsoft.VisualBasic.FileIO.MalformedLineException
            MsgBox("Line " & ex.Message & _
            " is invalid.  Skipping")
        End Try
    End While
End Using

This example depends on the existence of a function, processFields, which processes the fields as they are read.

Namespace: Microsoft.VisualBasic.FileIO

Class: TextFieldParser

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

Tasks

Concepts

Reference