File I/O

Code

' Write all text
System.IO.File.WriteAllText("output.txt", "Hello")

' Read all text
Dim content As String = System.IO.File.ReadAllText("input.txt")

' Append
System.IO.File.AppendAllText("log.txt", $"[{Date.Now}] Event{Environment.NewLine}")

' Read lines
For Each line As String In System.IO.File.ReadLines("data.txt")
    Console.WriteLine(line)
Next

' My.Computer.FileSystem (VB shortcut)
If My.Computer.FileSystem.FileExists("data.txt") Then
    Dim text As String = My.Computer.FileSystem.ReadAllText("data.txt")
    My.Computer.FileSystem.WriteAllText("copy.txt", text, False)
End If

' Binary
Dim bytes() As Byte = System.IO.File.ReadAllBytes("image.png")
System.IO.File.WriteAllBytes("copy.png", bytes)

Explanation

System.IO.File provides static methods for text/binary I/O. My.Computer.FileSystem is a VB-specific shortcut with the same capabilities. ReadAllText is simplest for small files; for large files use StreamReader/StreamWriter. ReadLines is lazy (iterates), ReadAllLines is eager (array).

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