[RESOLVED] Extract filename from textbox

I want to extract filename from textbox´s filepath, but it does not work.
InputFile is read-only textbox.
I´ve tried:

Code:

---

Dim nazovsuboru As String = IO.Path.GetFileNameWithoutExtension(InputFile.Text)
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        MsgBox(nazovsuboru)
    End Sub

---

Error: An error occurred creating the form. See Exception.InnerException for details. The error is: Object reference not set to an instance of an object.

I´ve looked at many different solutions, but none of that works for me. Thanks a lot.

Move the variable declaration inside the Sub.

Variables declared outside of routines are created when the form is first created, and any value assigned will happen at that time (not when the button is pressed). That means the value will only be correct if it would have been correct before the user could see the form.

On top of that, due to the way forms are created, the textbox doesn't exist at the time you are setting the variable (and that is what is giving the error).


Moving the variable declaration (or just the part that sets the value) inside the sub fixes both of those issues.

As si suggests, you definitely need to at least move the assignment, if not the declaration, inside the event handler:

vb.net Code:

Dim nazovsuboru As String
 
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
    nazovsuboru = IO.Path.GetFileNameWithoutExtension(InputFile.Text)
 
    MessageBox.Show(nazovsuboru)
End Sub

If you need to use that same variable in some other method as well, or it needs to retain its value between invocations of that one method, then that's what you should do. If the variable is only used in that one method and it doesn't have to retain its value between calls, declare the variable inside the method too. In that case, the variable ceases to exist when the method completes and starts existing again the next time that method is called.

Thanks jmcillhinney! It works now!