C#

textBox_taskMsg.Text = "Task is being performed.. This may take some time.";

string[] files = { textBox_Source1.Text, textBox_Source2.Text }; // Vids to be merged
string output = textBox_Source1.Text + "_merged.mp4"; // Output vid name
var conversion = await FFmpeg.Conversions.FromSnippet.Concatenate(output, files); // Merge
await conversion.Start();

// SHOW MERGING PROGRESS

textBox_taskMsg.Text = "Merge Complete.";

--------
//Create a string array to store file paths
string[] filepaths = new string[10];
filepaths.SetValue(textBox_Source1.Text, 0);
filepaths.SetValue(textBox_Source2.Text, 1);
//Call the video merging function
MergeVideos(filepaths, filepaths[0] + "_merged");

------
using (ITimeline timeline = new DefaultTimeline())
{
    IGroup group = timeline.AddVideoGroup(32, 720, 576); // Set bitrate, width, height

    var firstClip = group.AddTrack().AddVideo(videoPaths[0]);
    var secondClip = group.AddTrack().AddVideo(videoPaths[1], firstClip.Duration /* offset */);

    using (AviFileRenderer renderer = new AviFileRenderer(timeline, outputFilePath))
    {
        renderer.Render();
    }
}

try
{
    _clientContext = new ClientContext(baseUrl);
    _clientContext.Credentials = new SharePointOnlineCredentials(userName, Password.GetSecureString(password));
    _clientContext.Load(_clientContext.Web, w => w.ServerRelativeUrl);
    _clientContext.ExecuteQuery();
}
catch (Exception e)
{
    throw;
}