Post multiple files and form values using .NET (console application)

I want to POST multiple files and form variables to a CGI script, all in one HTTP request. I believe this requires a HTTP post with multipart/form-data encoding. Here is a sample HTML form that sends the required information; I need to send the same information through the application:

<form action="/process.php" enctype="multipart/form-data" method="post">
<input type="text" name="foo" value="bar">
<input type="text" name="blah" value="baz">
<input type="file" name="file1">
<input type="file" name="file2">
<input type="file" name="file3">
</form>

Please note that the application is a C# .NET GUI (or console) application, not an ASP.Net application.