Getting length of video

Here is an example:

using DirectShowLib;
using DirectShowLib.DES;
using System.Runtime.InteropServices;

...

var mediaDet = (IMediaDet)new MediaDet();
DsError.ThrowExceptionForHR(mediaDet.put_Filename(FileName));

// find the video stream in the file
int index;
var type = Guid.Empty;
for (index = 0; index < 1000 && type != MediaType.Video; index++)
{
    mediaDet.put_CurrentStream(index);
    mediaDet.get_StreamType(out type);
}

// retrieve some measurements from the video
double frameRate;
mediaDet.get_FrameRate(out frameRate);

var mediaType = new AMMediaType();
mediaDet.get_StreamMediaType(mediaType);
var videoInfo = (VideoInfoHeader)Marshal.PtrToStructure(mediaType.formatPtr, typeof(VideoInfoHeader));
DsUtils.FreeAMMediaType(mediaType);
var width = videoInfo.BmiHeader.Width;
var height = videoInfo.BmiHeader.Height;

double mediaLength;
mediaDet.get_StreamLength(out mediaLength);
var frameCount = (int)(frameRate * mediaLength);
var duration = frameCount / frameRate;

The easist and flawless solution I found is to use MediaToolkit nuget package.

using MediaToolkit;

// a method to get Width, Height, and Duration in Ticks for video.
public static Tuple<int, int, long> GetVideoInfo(string fileName)
{
    var inputFile = new MediaToolkit.Model.MediaFile { Filename = fileName };
    using (var engine = new Engine())
    {
        engine.GetMetadata(inputFile);
    }

    // FrameSize is returned as '1280x768' string.
    var size = inputFile.Metadata.VideoData.FrameSize.Split(new[] { 'x' }).Select(o => int.Parse(o)).ToArray();

    return new Tuple<int, int, long>(size[0], size[1], inputFile.Metadata.Duration.Ticks);
}

The open-source tool MediaInfo provides comprehensive meta-data for media files and can be used easily from your own application in DLL form:

void* Hande=MediaInfo::OpenQuick("**FILENAME**", "**VERSION**;**APP_NAME**;**APP_VERSION**")
MediaInfo::Inform()

I have tried to get the video length in a bit different way :
Actually using Windows Media Player Component also, we can get the duration of the video.
Following code snippet may help you guys :

using WMPLib;
// ...
var player = new WindowsMediaPlayer();
var clip = player.newMedia(filePath);
Console.WriteLine(TimeSpan.FromSeconds(clip.duration));

and don't forget to add the reference of wmp.dll which will be present in System32 folder.

you can get all sorts of information about many types of video formats including their duration with ffmpeg by using the -i flag:

ffmpeg -i videofile.whatever

If you want a nice library that can wrap ffmpef for you in C# then you can use MediaHandlerPro