Solve a signature error in csharp sample

I'm getting an oauth signature error with requests generated by the c# sample. SimpleOAuth.Utilities.UrlHelper.Encode seems to be leading to double url encoding, and one possible fix that works for me is to remove it. Eg - $query.ToString() returns location=San+Francisco%2c+CA (so, already url encoded) in the below.

PS C:\> add-type -assemblyname system.web
PS C:\> $query = [Web.HttpUtility]::ParseQueryString("")
PS C:\> $query["location"] = "San Francisco, CA"
PS C:\> $query.ToString()
location=San+Francisco%2c+CA
PS C:\> $uriBuilder = new-object UriBuilder("http://foo")
PS C:\> $uriBuilder.Query = $query.ToString()
PS C:\> $uriBuilder.ToString()
http://foo:80/?location=San+Francisco%2c+CA