How can I connect to video capture driver without creating a capture window. Is this possible ? In the other word, I want to capture video from user webcam without showing preview window.
You need to have a window only with legacy Video for Windows API. With DirectShow or Media Foundation, window is not necessary for video capture. In C# you can interface to those APIs using open source DirectShow.NET and Media Foundation.NET libraries.
FYI: DirectShow.NET includes CapWMV sample in C# that captures video into file.
A .NET sample application using the WM ASF Writer filter to create an wmv file While the underlying libraries are covered by LGPL, this sample is released as public domain. It is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.