TextFieldParser.PeekChars Method
Reads the specified number of characters without advancing the cursor.
' Usage
Dim value As String = TextFieldParserObject.PeekChars(numberOfChars)
' Declaration
Public Function PeekChars( _
ByVal numberOfChars As Integer _
) As String
Parameters
- numberOfChars
Int32. Number of characters to read. Required.
Return Value
String.
Exceptions
The following condition may cause an exception to be thrown:
- numberOfChars is less than 0 (ArgumentException).
Remarks
The numberOfChars value must be less than the total number of characters in the line. If it is not, the string returned by PeekChars will be truncated to the length of the line.
Blank lines are ignored.
End-of-line characters are not returned.
The PeekChars method performs no parsing; an end-of- line character within a delimited field is interpreted as the actual end of the line.
Tasks
The following table lists examples of tasks involving the PeekChars method.
To |
See |
|---|---|
Determine the format of a field before parsing it |
How to: Read From Text Files with Multiple Formats in Visual Basic |
Example
This example uses PeekChars to find the end of the data and stop parsing the file at that point.
Using MyReader As New Microsoft.VisualBasic.FileIO.TextFieldParser("C:\ParserText.txt")
MyReader.TextFieldType = Microsoft.VisualBasic.FileIO.FieldType.Delimited
MyReader.Delimiters = New String() {","}
MyReader.CommentTokens = New String() {"'"}
Dim currentRow As String()
While (MyReader.PeekChars(1) IsNot "")
Try
currentRow = MyReader.ReadFields()
For Each currentField As String In currentRow
My.Computer.FileSystem.WriteAllText _
("C://testfile.txt", currentField, True)
Next
Catch ex As Microsoft.VisualBasic.FileIO.MalformedLineException
MsgBox("Line " & ex.Message & " is invalid. Skipping")
End Try
End While
End Using
Requirements
Namespace:Microsoft.VisualBasic.FileIO
Class:TextFieldParser
Assembly: Visual Basic Runtime Library (in Microsoft.VisualBasic.dll)
Permissions
The following permissions are required:
Permission |
Description |
|---|---|
Controls the ability to access files and folders. Associated enumeration: Unrestricted. |
|
Describes a set of security permissions applied to code. Associated enumeration: ControlEvidence. |
For more information, see Code Access Security and Requesting Permissions.
See Also
Concepts
Parsing Text Files with the TextFieldParser Object