WebClient.Downloadfile API is not working in powershell - powershell-2.0

Question

(new-object System.Net.WebClient).Downloadfile("https://www.dropbox.com/sh/tsyz48qg0rq3smz/QAstBLgPgN/version.txt", "C:\Users\Brangle\Desktop\version.txt") API download invalid data.
version.txt file need to download. But actually it is downloading some xml file contains in version.txt on destination location
Thanks in advance

Answer 1

You are trying to download the dropbox page which presents your file in a nice dropbox-themed html. You need to extract the real url and can do so using the following code:
$wc = New-Object system.net.webclient;
$s = $wc.downloadString("https://www.dropbox.com/sh/tsyz48qg0rq3smz/QAstBLgPgN/version.txt");
$r = [regex]::matches($s, "https://.*token_hash.*(?=`")");
$realURL = $r[$r.count-1].Value;
$wc.Downloadfile($realURL, "U:\version.txt");
The regex part looks for a url starting https://, has a string token_hash in the middle and ends one character before double quotes character ". The line in question is:
FilePreview.init_text("https://dl.dropboxusercontent.com/sh/tsyz48qg0rq3smz/QAstBLgPgN/version.txt?token_hash=AAEGxMpsE-T4xodBPd3A6uPTCr0uqh7h4B2YUSmTDJHmjg", 0, null, 0)
Hope this helps.

Answer 2

Here is the function:
function download-dropbox($Url, $FilePath) {
$wc = New-Object system.net.webclient
$req = [System.Net.HttpWebRequest]::Create($Url)
$req.CookieContainer = New-Object System.Net.CookieContainer
$res = $req.GetResponse()
$cookies = $res.Cookies | % { $_.ToString()}
$cookies = $cookies -join '; '
$wc.Headers.Add([System.Net.HttpRequestHeader]::Cookie, $cookies)
$newurl = $url + '?dl=1'
mkdir (Split-Path $FilePath) -force -ea 0 | out-null
$wc.downloadFile($newurl, $tempFile)
}

Answer 3

Re: LogMeIn - theyuse a cookie base authentication so you can't use the previous code. Try this, it gets a cookie from the first response and then uses that to download using webclient:
$url = "https://secure.logmein.com/fileshare.asp?ticket=01_L5vwmOrmsS3mnxPO01f5FRbWUwVKlfheJ5HsfpTV"
$wc = New-Object system.net.webclient
$req = [System.Net.HttpWebRequest]::Create($url)
$req.CookieContainer = New-Object System.Net.CookieContainer
$res = $req.GetResponse()
$cookie = $res.Cookies.Name + "=" + $res.Cookies.Value
$wc.Headers.Add([System.Net.HttpRequestHeader]::Cookie, $cookie)
$newurl = $url + "`&download=1"
$wc.downloadFile($newurl, "c:\temp\temp.zip")