Exception thrown: 'System.IO.FileNotFoundException' in Hotel.dll - oracle

Question

I'm a beginner to using vb.net, on this issue I want to connect Oracle 12c to my visual basic application. I think everything is correct, and the application can also be run. but when i want to test the connection, my console displays an error Exception thrown: 'System.IO.FileNotFoundException' in Hotel.dll
Here is my code :
Imports Oracle.DataAccess.Client
Public Class Form1
Dim con As New OracleConnection
Dim cmd As New OracleCommand
Dim sql As String
Private Sub btntest_Click(sender As Object, e As EventArgs) Handles btntest.Click
dbAccess()
End Sub
Private Sub dbAccess()
con = New OracleConnection
Try
con.ConnectionString = "Data Source=(DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))(CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = pdborcl))); user id=admin;password=admin"
con.Open()
MsgBox("Connection OK")
Catch ex As Exception
MsgBox("Connection Fail")
End Try
End Sub
End Class
Here is the error :
https://i.ibb.co/443qTQ0/Untitled.png
https://i.ibb.co/84D8Rty/Untitledx.png

Answer 1

Connection and commands need to be declared locally in Using blocks in the method where they are used. They contain unmanaged resources which the class releases in a Dispose method. Using blocks close and dispose these objects even if there is an error.
Calling ToString on the Exception should give you more details on the problem.
For connection problems see https://www.connectionstrings.com/oracle-data-provider-for-net-odp-net/
Private OracleConstring As String = "Data Source=(DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT = 1521))(CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = pdborcl))); user id=admin;password=admin"
Private Sub dbAccess()
Using con As New OracleConnection(OracleConstring)
Try
con.Open()
MsgBox("Connection OK")
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Using
End Sub