ASP.NET

Visual Basic  
Protected Sub Page_Load(ByVal sender As Object, 
        ByVal e As System.EventArgs) Handles Me.Load
    If IsPostBack Then
        Dim path As String = Server.MapPath("~/UploadedImages/")
        Dim fileOK As Boolean = False
        If FileUpload1.HasFile Then
            Dim fileExtension As String
            fileExtension = System.IO.Path. _
                GetExtension(FileUpload1.FileName).ToLower()
            Dim allowedExtensions As String() = _
                {".jpg", ".jpeg", ".png", ".gif"}
            For i As Integer = 0 To allowedExtensions.Length - 1
                If fileExtension = allowedExtensions(i) Then
                   fileOK = True
                End If
            Next
            If fileOK Then
                Try
                    FileUpload1.PostedFile.SaveAs(path & _
                         FileUpload1.FileName)
                    Label1.Text = "File uploaded!"
                Catch ex As Exception
                    Label1.Text = "File could not be uploaded."
                End Try
            Else
                Label1.Text = "Cannot accept files of this type."
            End If
        End If
    End If
End Sub