Reading a filestream issue

This line is wrong

Dim buffer() As Byte = New Byte() {fileLength} 

It declares an array of 1 byte in which you try to store the length of your file. Probably you have Option Strict set to Off and thus you could go away without noticing immediately the problem.

Of course, if your file is of a reasonable length and it is a simple textfile then there is no need for this loop. Just use File.ReadAllText or File.ReadLines or File.ReadAllLines, and by the way, your code read all your data in a single call because the last parameter of FileStream.Read is the quantity of bytes to read from file and the expression fileLength - sum produces a request to read all the bytes in a single call

Instead if you want to read your file in chunks of certain sizes then probably you need

Using fs As New FileStream(path, FileMode.Open, FileAccess.Read) Try Dim chunkSize = 2000 Dim fileLength As Integer = CInt(fs.Length) Dim buffer(fileLength) as Byte Dim blockSize(chunkSize) as Byte Dim count As Integer = -1 Dim pos As Integer = 0 While count <> 0 count = fs.Read(blockSize, 0, chunkSize-1) Array.Copy(blockSize, 0, buffer, pos, count) pos += count End While litOutput.Text = Encoding.UTF8.GetString(buffer) Catch ex As Exception Console.WriteLine(ex.Message) End Try End Using 

Notice that this code assumes that your file is a Text file with UTF8 encoding.
It this is not the case then you could try with Encoding.ASCII.GetString or Encoding.Unicode.GetString