How to select a file in a web app

I have a web app and am working in VB.Net.  

On one of the pages of my web site, I need to allow the user to select a file, after which I will import the data and work with it.  I already have the import logic working, but now I need logic to present the typical file dialog to allow the user to select the file.

I have attached the code I am having trouble with -- it needs to simply ask the user to locate and select a file.  If the user does so, I will store the complete path in "Import_FileLabel"

I have so far tried the attached code, but am getting an error:

"Showing a modal dialog box or form when the application is not running in UserInteractive mode is not a valid operation. Specify the ServiceNotification or DefaultDesktopOnly style to display a notification from a service application."

How do I modify the code to work, or alternatively, what code should I be using?Start Free Trial

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Protected Sub Select_a_Template_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Select_a_Template.Click
        Dim openfile As New Windows.Forms.OpenFileDialog
 
        openfile.CheckFileExists = True
        openfile.CheckPathExists = True
        openfile.Filter = "Excel Files (*.xls)|*.xls|Other Files|*.*"
        openfile.ShowDialog()
 
        If openfile.FileName <> "" Then
            Me.Import_FileLabel.Text = openfile.FileName.ToString()
        Else
            Me.Import_FileLabel.Text = "No file currently selected."
        End If
    End Sub