Visual Basic InputBox closing error - vb.net

Question

This is a bit of a weird question, and apologies for the vast amount of code the question contains, but, I've been given somebody else's project to maintain, and the user has come to me with an error. There is a button which opens the InputBox, seen below.
The form is used to enter a path of a file to import. If the user enters no path, or an incorrect one, an error is displayed - fine. Now, the problem is, is that if the user presses the 'Cancel' button or the x in the top right to close the form, it also returns the same error, saying that the path cannot be found.
After looking through the following code, I can't work out how to make it so that the error is not displayed when pressing the x or Cancel, so can anybody help me out at all?
Private Sub btnImport_Click(sender As Object, e As EventArgs) Handles btnImport.Click
Try
Dim importbox As String = InputBox("Input path", "Import", "")
Dim fi As New FileInfo(importbox)
Dim connectionString As String = "Provider=Microsoft.Jet.OLEDB.4.0;Extended Properties=Text;Data Source=" & fi.DirectoryName
Dim conn As New OleDbConnection(connectionString)
conn.Open()
Dim add1 As String = ""
Dim add2 As String = ""
Dim add3 As String = ""
Dim add4 As String = ""
Dim add5 As String = ""
Dim postcode As String = ""
Dim telephone As String = ""
Dim fax As String = ""
Dim email As String = ""
Dim customercode As String = ""
Dim customername As String = ""
Dim webpage As String = ""
Dim mobile As String = ""
Dim headerTable As DataTable = ugHeaders.DataSource
Dim csvArray(headerTable.Rows.Count) As String
Dim i As Integer = 0
For Each dr As DataRow In headerTable.Rows
csvArray(i) = dr.Item("CSVName")
Next
For Each dr As DataRow In headerTable.Rows
Select Case dr.Item("DBName").ToString.Trim
Case "Add1"
add1 = dr.Item("CSVName")
Case "Add2"
add2 = dr.Item("CSVName")
Case "Add3"
add3 = dr.Item("CSVName")
Case "Add4"
add4 = dr.Item("CSVName")
Case "Add5"
add5 = dr.Item("CSVName")
Case "PostCode"
postcode = dr.Item("CSVName")
Case "Telephone"
telephone = dr.Item("CSVName")
Case "Fax"
fax = dr.Item("CSVName")
Case "Email"
email = dr.Item("CSVName")
Case "Customer_Name"
customername = dr.Item("CSVName")
Case "Customer_Code"
customercode = dr.Item("CSVName")
Case "webpage"
webpage = dr.Item("CSVName")
Case "mobile_phone"
mobile = dr.Item("CSVName")
End Select
Next
Dim sqlSelect As String = "SELECT Company, [" & add1 & "], [" & add3 & "], [" & postcode & "], [" & add2 & "], " & _
"[" & telephone & "], [" & fax & "], [" & email & "], [" & customercode & "], " & _
"[" & add4 & "], [" & add5 & "], [" & webpage & "], [" & mobile & "] FROM " & fi.Name
Dim cmdSelect As New OleDbCommand(sqlSelect, conn)
Dim adapter1 As New OleDbDataAdapter(cmdSelect)
Dim ds As New DataSet
adapter1.Fill(ds, "DATA")
pb_progress.Maximum = ds.Tables(0).Rows.Count
pb_progress.Value = 0
For Each dr As DataRow In ds.Tables(0).Rows
Try
Debug.WriteLine(dr.Item(customercode).ToString.Trim)
If dr.Item(customercode).ToString.Trim = "" Then
Dim str As String = dr.Item(customername)
If str.Trim = "" Then Continue For
Dim length As Integer = str.Length
If length < 20 Then
Else
length = 20
End If
str = Replace(str.Substring(0, length), " ", "_").ToUpper
str = Regex.Replace(str, "[^a-zA-Z _&]", "")
Dim found As Boolean = True
Dim loopcount As Integer = 1
Do Until found = False
Dim checkSql As String = "SELECT * FROM Customers WHERE [Customer_Code] = #ccode"
Dim checkCmd As New OleDb.OleDbCommand(checkSql, con)
checkCmd.Parameters.AddWithValue("#ccode", str)
Dim checkDa As New OleDb.OleDbDataAdapter(checkCmd)
Dim checkDt As New DataTable
checkDa.Fill(checkDt)
If checkDt.Rows.Count <> 0 Then
found = True
str &= CStr(loopcount)
loopcount += 1
Else
found = False
End If
Loop
dr.Item(customercode) = str
Else
Dim found As Boolean = True
Dim loopcount As Integer = 1
Do Until found = False
Dim checkSql As String = "SELECT * FROM Customers WHERE [Customer_Code] = #ccode"
Dim checkCmd As New OleDb.OleDbCommand(checkSql, con)
checkCmd.Parameters.AddWithValue("#ccode", dr.Item(customercode))
Dim checkDa As New OleDb.OleDbDataAdapter(checkCmd)
Dim checkDt As New DataTable
checkDa.Fill(checkDt)
If checkDt.Rows.Count <> 0 Then
found = True
dr.Item(customercode) &= CStr(loopcount)
loopcount += 1
Else
found = False
End If
Loop
End If
Dim sql As String
sql = "INSERT INTO Customers(Customer_Code, Customer_Name, Contract_Payment_Terms, Aq_Date, Telephone, Fax, Email, Average_Payment_Terms, webpage, mobile_phone) " & _
"VALUES(#ccode, #cname, 30, #01/01/2016#, #ctele, #cfax, #email, 30, #webpage, #mobile);"
Dim cmd As New OleDb.OleDbCommand(sql, con)
With cmd.Parameters
.AddWithValue("#ccode", dr.Item(customercode))
.AddWithValue("#cname", dr.Item(customername))
.AddWithValue("#ctele", dr.Item(telephone).ToString.Truncate(48))
.AddWithValue("#cfax", dr.Item(fax))
.AddWithValue("#email", dr.Item(email))
.AddWithValue("#webpage", dr.Item(webpage))
.AddWithValue("#mobile", dr.Item(mobile))
End With
cmd.ExecuteNonQuery()
sql = "INSERT INTO [Customer_Addresses] (Cust_Code, PostCode, Alias, Add1, Add2, Add3, Add4, Add5) VALUES(#ccode, #pcode, 'Default'" & _
",#add1, #add2, #add3, #add4, #add5);"
cmd = New OleDb.OleDbCommand(sql, con)
With cmd.Parameters
.AddWithValue("#ccode", dr.Item(customercode))
.AddWithValue("#pcdoe", dr.Item(postcode))
.AddWithValue("#add1", dr.Item(add1))
.AddWithValue("#add2", dr.Item(add2))
.AddWithValue("#add3", dr.Item(add3))
.AddWithValue("#add4", dr.Item(add4))
.AddWithValue("#add5", dr.Item(add5))
End With
cmd.ExecuteNonQuery()
Catch ex As Exception
Debug.WriteLine(ex.Message)
End Try
pb_progress.Increment(1)
Next
MsgBox("Import successful", MsgBoxStyle.OkOnly, "Success")
Catch ex As Exception
errorLog(ex)
End Try
End Sub

Answer 1

Inputbox will always return a String.
If the Users presses "OK" it will return the String put into the TextBox.
If he cancels the box by pressing X or Cancel it returns "".
I would generally not recommend using an Inputbox for getting a filepath. Use an OpenFileDialog instead. If you have the fullpath already in your Clipboard you can just paste it into the Filename-Textboxof the OFD and press enter.
This should get you started:
Dim ofd as new OpenFileDialog()
// Show the File Dialog to the user and detect he pressed OK or Cancelled
if ofd.ShowDialog = Windows.Forms.DialogResult.OK
// Always check, if the file really exists
if IO.File.exists(ofd.FileName)
importbox = ofd.FileName
Else
msgbox("File does not exist")
Exit Sub
End if
Else
Exit Sub
End if