How to put this to .NET code?

[PT Exorcist]

Private Declare Function URLDownloadToFile Lib "urlmon" Alias "URLDownloadToFileA" (ByVal pCaller As Long, ByVal szURL As String, ByVal szFileName As String, ByVal dwReserved As Long, ByVal lpfnCB As Long) As Long
Public Function DownloadFile(URL As String, LocalFilename As String) As Boolean
Dim lngRetVal As Long
lngRetVal = URLDownloadToFile(0, URL, LocalFilename, 0, 0)
If lngRetVal = 0 Then DownloadFile = True
End Function
Private Sub Form_Load()
DownloadFile "http://www.allapi.net", "c:\allapi.htm"
End Sub

how do i put this to .NET code? i already tryed but it seems to take no effect