What's the best way to get video metadata from a video file in ASP.Net MVC using C#?

Have a look at MediaInfo project (http://mediaarea.net/en/MediaInfo)

it gets extensive information about most media types, and the library is bundled with a c# helper class which is easy to use.

You can download the library and helper class for windows from here:

http://mediaarea.net/en/MediaInfo/Download/Windows (DLL without installer)

The helper class is located at Developers\Source\MediaInfoDLL\MediaInfoDLL.cs, simply add it to your project and copy the MediaInfo.dll to your bin.

Usage

you can obtain information by requesting specific parameter from the library, Here is a sample:

[STAThread]
static void Main(string[] Args)
{
    var mi = new MediaInfo();
    mi.Open(@"video path here");

    var videoInfo = new VideoInfo(mi);
    var audioInfo = new AudioInfo(mi);
     mi.Close();
}

public class VideoInfo 
{
    public string Codec { get; private set; }
    public int Width { get; private set; }
    public int Heigth { get; private set; }
    public double FrameRate { get; private set; }
    public string FrameRateMode { get; private set; }
    public string ScanType { get; private set; }
    public TimeSpan Duration { get; private set; }
    public int Bitrate { get; private set; }
    public string AspectRatioMode { get; private set; }
    public double AspectRatio { get; private set; }

    public VideoInfo(MediaInfo mi)
    {
        Codec=mi.Get(StreamKind.Video, 0, "Format");
        Width = int.Parse(mi.Get(StreamKind.Video, 0, "Width"));
        Heigth = int.Parse(mi.Get(StreamKind.Video, 0, "Height"));
        Duration = TimeSpan.FromMilliseconds(int.Parse(mi.Get(StreamKind.Video, 0, "Duration")));
        Bitrate = int.Parse(mi.Get(StreamKind.Video, 0, "BitRate"));
        AspectRatioMode = mi.Get(StreamKind.Video, 0, "AspectRatio/String"); //as formatted string
        AspectRatio =double.Parse(mi.Get(StreamKind.Video, 0, "AspectRatio"));
        FrameRate = double.Parse(mi.Get(StreamKind.Video, 0, "FrameRate"));
        FrameRateMode = mi.Get(StreamKind.Video, 0, "FrameRate_Mode");
        ScanType = mi.Get(StreamKind.Video, 0, "ScanType");
    }
}

public class AudioInfo
{
    public string Codec { get; private set; }
    public string CompressionMode { get; private set; }
    public string ChannelPositions { get; private set; }
    public TimeSpan Duration { get; private set; }
    public int Bitrate { get; private set; }
    public string BitrateMode { get; private set; }
    public int SamplingRate { get; private set; }

    public AudioInfo(MediaInfo mi)
    {
        Codec = mi.Get(StreamKind.Audio, 0, "Format");
        Duration = TimeSpan.FromMilliseconds(int.Parse(mi.Get(StreamKind.Audio, 0, "Duration")));
        Bitrate = int.Parse(mi.Get(StreamKind.Audio, 0, "BitRate"));
        BitrateMode = mi.Get(StreamKind.Audio, 0, "BitRate_Mode");
        CompressionMode = mi.Get(StreamKind.Audio, 0, "Compression_Mode");
        ChannelPositions = mi.Get(StreamKind.Audio, 0, "ChannelPositions");
        SamplingRate = int.Parse(mi.Get(StreamKind.Audio, 0, "SamplingRate"));
    }
}

You can easily obtain all information in string format by callingInform():

        var mi = new MediaInfo();
        mi.Open(@"video path here");
        Console.WriteLine(mi.Inform());
        mi.Close();

if you need more information about available parameters, you can simply query all of them by calling Options("Info_Parameters"):

        var mi = new MediaInfo();
        Console.WriteLine(mi.Option("Info_Parameters"));
        mi.Close();

It may be little late... You can do this with minimal code using the NuGet package of MediaToolKit

For more info get going from here MediaToolKit

I suggest you use ffmpeg with Process.Start, the code looks like follows:

    private string GetVideoDuration(string ffmpegfile, string sourceFile) {
        using (System.Diagnostics.Process ffmpeg = new System.Diagnostics.Process()) {
            String duration;  // soon will hold our video's duration in the form "HH:MM:SS.UU"
            String result;  // temp variable holding a string representation of our video's duration
            StreamReader errorreader;  // StringWriter to hold output from ffmpeg

            // we want to execute the process without opening a shell
            ffmpeg.StartInfo.UseShellExecute = false;
            //ffmpeg.StartInfo.ErrorDialog = false;
            ffmpeg.StartInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
            // redirect StandardError so we can parse it
            // for some reason the output comes through over StandardError
            ffmpeg.StartInfo.RedirectStandardError = true;

            // set the file name of our process, including the full path
            // (as well as quotes, as if you were calling it from the command-line)
            ffmpeg.StartInfo.FileName = ffmpegfile;

            // set the command-line arguments of our process, including full paths of any files
            // (as well as quotes, as if you were passing these arguments on the command-line)
            ffmpeg.StartInfo.Arguments = "-i " + sourceFile;

            // start the process
            ffmpeg.Start();

            // now that the process is started, we can redirect output to the StreamReader we defined
            errorreader = ffmpeg.StandardError;

            // wait until ffmpeg comes back
            ffmpeg.WaitForExit();

            // read the output from ffmpeg, which for some reason is found in Process.StandardError
            result = errorreader.ReadToEnd();

            // a little convoluded, this string manipulation...
            // working from the inside out, it:
            // takes a substring of result, starting from the end of the "Duration: " label contained within,
            // (execute "ffmpeg.exe -i somevideofile" on the command-line to verify for yourself that it is there)
            // and going the full length of the timestamp

            duration = result.Substring(result.IndexOf("Duration: ") + ("Duration: ").Length, ("00:00:00").Length);
            return duration;
        }
    }

May it helps.