breaking out of sub after if statement in vb.net - vb.net

Question

I am trying to write code that opens the saveFileDialog only if the variable 'file' is not empty and generates an error message if 'file' is empty. The following code will pop up a error message box when 'file' is empty but will proceed to open the saveFileDialog anyway.
Public Shared Sub DownloadFile(cloudId As CloudIdentity, directoryPath As String, file As String)
Try
Dim cloudFilesProvider = New CloudFilesProvider(cloudId)
If file = "" Then
cloudFilesProvider.GetObjectSaveToFile("EstherTest", directoryPath, file)
End If
Catch
If file = "" Then
MessageBox.Show("Please select file to view")
End If
End Try
End Sub
Can you please direct me.

Answer 1

I think you have the wrong equality operator in your first if-statement.
In humand words, you are telling the compiler:
If file is equal to "" then do ... (If file = "" Then)
What you are trying to say is: if file is NOT equal to "" (If file <> "" Then).
As a second note: Unless an exception occurs, your second if statement will never be called, because the catch block will never be reached. You should put the second clause in a else or else if clause.
I've removed the try catch block for simplicity (and because I'm not really good at the vb.net syntax).
All in all your code should look like this:
Public Shared Sub DownloadFile(cloudId As CloudIdentity, directoryPath As String, file As String)
Dim cloudFilesProvider = New CloudFilesProvider(cloudId)
' if file is not emtpy, proceed
If file <> "" Then
cloudFilesProvider.GetObjectSaveToFile("EstherTest", directoryPath, file)
' else if file is empty, show message box
else if file = "" Then
MessageBox.Show("Please select file to view")
End If
End Sub