How to check if sub-folder text file exists - vb.net

Question

I am trying to search if a text file in a sub-folder exists.
This is the code I am using:
'Checks the program's root folder to see if the root folder exists.
Dim FolderName = New DirectoryInfo(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "Cake Orders\" & TextBox1.Text))
Dim McKnwoll As String = Path.Combine(FolderName.FullName, Trim(TextBox2.Text) & (" ") & Trim(TextBox3.Text) + ".RTO")
If Not McKnwoll.Exists Then
‘Message to user that file does not exist in sub-folder
Else
‘Message to user that file does exists in sub-folder
End If
I am getting an error that 'Exists' is not a member of 'String'. How can I re-work my code to check if the text file whose name is in the format of "TextBox2.Text & (" ") & TextBox3.Text + ".RTO"; exists.
I am using Visual Basic 2010 Express. Thank you.

Answer 1

File.Exists returns a Boolean indicating whether a file at a certain path exists:
If File.Exists(pathToFile) Then
...
End If
Be sure to include Imports System.IO at the top of your source code file.

Answer 2

You seem quite new in programming. Welcome.
That error message you got ('Exists' is not a member of 'String') tells you exactely what is wrong: You try to ask a string (some text) whether it exists, but what you like to do is to ask a file whether it exists.
The class that provides information about a file is called "FileInfo", and FileInfo has an "Exists" property that you can call:
Dim myFileInfo As New FileInfo(McKnwoll)
If myFileInfo.Exists Then
'do something
End If
That's the object oriented answer, Heinzi's more service oriented one but works, of course, too.
There have been several other small issues I noticed with your code, e.g.
"Cake Orders\" & TextBox1.Text
does not use Path.Combine but makes a string concatenation using fix a "\" as directory separater. Or that the DirectoryInfo is not really used here, the string to the folder is enough.
You also try to handle 3 different issues (reading the values from the user interface, constructing the fullname of the file, checking whether the file exists) in one single code block. I would split them into 3 different ones (actually 4, I would add another one for displaying error messages).
Your simple few lines of codes could be complicated like this ;-)
Imports System.IO
Imports System.Text
Public Class Form1
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
ReadFileIfPossible(TextBox1.Text, TextBox2.Text, TextBox3.Text)
End Sub
Private Sub ReadFileIfPossible(subfolder As String, part1 As String, part2 As String)
'Get the path to the RTO file
Dim myFilePath As String = Nothing
Try
myFilePath = GetRtoFilePath(subfolder, part1, part2)
Catch ex As Exception
DisplayErrorMessage("Error constructing file name! Please check the values of TextBox1, TextBox2 and TextBox3.")
Return
End Try
'Get the file info
Dim myFile As FileInfo = Nothing
Try
myFile = New FileInfo(myFilePath)
Catch ex As Exception
DisplayErrorMessage(ex.Message)
Return
End Try
'Check whether it exists
Dim myExists As Boolean = False
Try
myExists = myFile.Exists 'it's IO, everything might throw an exception...
Catch ex As Exception
DisplayErrorMessage(ex.Message)
Return
End Try
'Display message if not found
If (Not myExists) Then
DisplayErrorMessage("File ""{0}"" could not be found!", myFilePath)
Return
End If
'Read the file
Dim myLines As String() = Nothing
Try
myLines = File.ReadAllLines(myFile.FullName, New UTF8Encoding(True))
Catch ex As Exception
DisplayErrorMessage(ex.Message)
Return
End Try
'Do something with it...
End Sub
Private Shared Function GetRtoFilePath(subfolder As String, part1 As String, part2 As String) As String
'Check args
If (subfolder Is Nothing) Then Throw New ArgumentNullException("subfolder")
If (part1 Is Nothing) Then Throw New ArgumentNullException("part1")
If (part2 Is Nothing) Then Throw New ArgumentNullException("part2")
'Normalize args
part1 = part1.Trim()
part2 = part2.Trim()
'Build path
Dim myDesktopPath As String = Environment.GetFolderPath(Environment.SpecialFolder.Desktop)
Dim myFolderPath As String = Path.Combine(myDesktopPath, "Cake Orders")
myFolderPath = Path.Combine(myFolderPath, subfolder)
Dim myFileName As String = String.Format("{0} {1}.RTO", part1, part2)
Dim myResult As String = Path.Combine(myFolderPath, myFileName)
myResult = Path.GetFullPath(myResult)
'Return result
Return myResult
End Function
Private Sub DisplayErrorMessage(message As String, ParamArray args As Object())
Dim myMsg As String = String.Format(message, CType(args, Object()))
MsgBox(myMsg, MsgBoxStyle.OkOnly, "Error")
End Sub
End Class
Have fun.