Question

I have following code:

Dim fs As FileStream
fs = New FileStream(path, FileMode.Create)

Dim sw As StreamWriter
sw = New StreamWriter(os)
sw.Write(something)
sw.Flush()

Is this a correct way to do this? Do i need to put in some checks to see if file exists?

Answer 1

Do i need to put in some checks to see if file exists?

It depends on what you are trying to do. If you want to overwrite the file, then no. FileMode.Create will always overwrite an existing file, or if it doesn’t exist, create it:

Create

Specifies that the operating system should create a new file. If the file already exists, it will be overwritten. This operation requires FileIOPermissionAccess.Write permission. System.IO.FileMode.Create is equivalent to requesting that if the file does not exist, use CreateNew; otherwise, use Truncate. If the file already exists but is a hidden file, an UnauthorizedAccessException exception is thrown.

If you don’t want to overwrite an existing file, then yes you should check it. Something like this:

If Not File.Exists(path) Then
    Using fs As New FileStream(path, FileMode.CreateNew), sw As New StreamWriter(fs)
        sw.Write("Something")
    End Using
End If

You’ll also notice that I used CreateNew instead of Create. This is an additional safety check to ensure that an existing file is never overwritten. With CreateNew, an exception is raised if the file already exists. You should still check if it exists however, since we don’t want the exception to happen in the first place.