File.ReadAllLines Method (String)

 

Opens a text file, reads all lines of the file, and then closes the file.

Namespace:   System.IO
Assembly:  mscorlib (in mscorlib.dll)

Public Shared Function ReadAllLines (
	path As String
) As String()

Parameters

path
Type: System.String

The file to open for reading.

Return Value

Type: System.String()

A string array containing all lines of the file.

Exception Condition
ArgumentException

path is a zero-length string, contains only white space, or contains one or more invalid characters as defined by InvalidPathChars.

ArgumentNullException

path is null.

PathTooLongException

The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.

DirectoryNotFoundException

The specified path is invalid (for example, it is on an unmapped drive).

IOException

An I/O error occurred while opening the file.

UnauthorizedAccessException

path specified a file that is read-only.

-or-

This operation is not supported on the current platform.

-or-

path specified a directory.

-or-

The caller does not have the required permission.

FileNotFoundException

The file specified in path was not found.

NotSupportedException

path is in an invalid format.

SecurityException

The caller does not have the required permission.

This method opens a file, reads each line of the file, then adds each line as an element of a string array. It then closes the file. A line is defined as a sequence of characters followed by a carriage return ('\r'), a line feed ('\n'), or a carriage return immediately followed by a line feed. The resulting string does not contain the terminating carriage return and/or line feed.

This method attempts to automatically detect the encoding of a file based on the presence of byte order marks. Encoding formats UTF-8 and UTF-32 (both big-endian and little-endian) can be detected.

The following code example demonstrates the use of the ReadAllLines method to display the contents of a file. In this example a file is created, if it doesn't already exist, and text is added to it.

Imports System
Imports System.IO

Public Class Test
    Public Shared Sub Main()
        Dim path As String = "c:\temp\MyTest.txt"
        Dim sw As StreamWriter

        ' This text is added only once to the file.
        If File.Exists(path) = False Then

            ' Create a file to write to.
            Dim createText() As String = {"Hello", "And", "Welcome"}
            File.WriteAllLines(path, createText)
        End If

        ' This text is always added, making the file longer over time
        ' if it is not deleted.
        Dim appendText As String = "This is extra text" + Environment.NewLine
        File.AppendAllText(path, appendText)

        ' Open the file to read from.
        Dim readText() As String = File.ReadAllLines(path)
        Dim s As String
        For Each s In readText
            Console.WriteLine(s)
        Next
    End Sub
End Class

FileIOPermission

for access to read from a file or directory. Associated enumeration: FileIOPermissionAccess.Read

Universal Windows Platform
Available since 10
.NET Framework
Available since 2.0
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