Notes

using System.IO;
using System.Drawing;
using System.Diagnostics;
using System.Drawing.Imaging;
using System.Collections.Generic;
using System.Runtime.InteropServices;

using Accord.Video.FFMPEG;

namespace BenScreenRecorder
{
class ScreenRecorder
{
//Video variables:
private Rectangle bounds;
private string outputPath = "";
private string tempPath = "";
private int fileCount = 1;
private List<string> inputImageSequence = new List<string>();

//File variables:
private string audioName = "mic.wav";
private string videoName = "video.mp4";
private string finalName = "FinalVideo.mp4";

//Time variable:
Stopwatch watch = new Stopwatch();

//Audio variables:
public static class NativeMethods
{
[DllImport("winmm.dll", EntryPoint = "mciSendStringA", ExactSpelling = true, CharSet = CharSet.Ansi, SetLastError = true)]
public static extern int record(string lpstrCommand, string lpstrReturnString, int uReturnLength, int hwndCallback);
}

//ScreenRecorder Object:
public ScreenRecorder(Rectangle b, string outPath)
{
//Create temporary folder for screenshots:
CreateTempFolder("tempScreenCaps");

//Set variables:
bounds = b;
outputPath = outPath;
}

//Create temporary folder:
private void CreateTempFolder(string name)
{
//Check if a C or D drive exists:
if (Directory.Exists("D://"))
{
string pathName = $"D://{name}";
Directory.CreateDirectory(pathName);
tempPath = pathName;
}
else
{
string pathName = $"C://Documents//{name}";
Directory.CreateDirectory(pathName);
tempPath = pathName;
}
}

//Change final video name:
public void setVideoName(string name)
{
finalName = name;
}

//Delete all files and directory:
private void DeletePath(string targetDir)
{
string[] files = Directory.GetFiles(targetDir);
string[] dirs = Directory.GetDirectories(targetDir);

//Delete each file:
foreach (string file in files)
{
File.SetAttributes(file, FileAttributes.Normal);
File.Delete(file);
}

//Delete the path:
foreach (string dir in dirs)
{
DeletePath(dir);
}

Directory.Delete(targetDir, false);
}

//Delete all files except the one specified:
private void DeleteFilesExcept(string targetDir, string excDir)
{
string[] files = Directory.GetFiles(targetDir);

//Delete each file except specified:
foreach (string file in files)
{
if(file != excDir)
{
File.SetAttributes(file, FileAttributes.Normal);
File.Delete(file);
}
}
}

//Clean up program on crash:
public void cleanUp()
{
if (Directory.Exists(tempPath))
{
DeletePath(tempPath);
}
}

//Return elapsed time:
public string getElapsed()
{
return string.Format("{0:D2}:{1:D2}:{2:D2}", watch.Elapsed.Hours, watch.Elapsed.Minutes, watch.Elapsed.Seconds);
}

//Record video:
public void RecordVideo()
{
//Keep track of time:
watch.Start();

using (Bitmap bitmap = new Bitmap(bounds.Width, bounds.Height))
{
using (Graphics g = Graphics.FromImage(bitmap))
{
//Add screen to bitmap:
g.CopyFromScreen(new Point(bounds.Left, bounds.Top), Point.Empty, bounds.Size);
}
//Save screenshot:
string name = tempPath + "//screenshot-" + fileCount + ".png";
bitmap.Save(name, ImageFormat.Png);
inputImageSequence.Add(name);
fileCount++;

//Dispose of bitmap:
bitmap.Dispose();
}
}

//Record audio:
public void RecordAudio()
{
NativeMethods.record("open new Type waveaudio Alias recsound", "", 0, 0);
NativeMethods.record("record recsound", "", 0, 0);
}

//Save audio file:
private void SaveAudio()
{
string audioPath = "save recsound " + outputPath + "//" + audioName;
NativeMethods.record(audioPath, "", 0, 0);
NativeMethods.record("close recsound", "", 0, 0);
}

//Save video file:
private void SaveVideo(int width, int height, int frameRate)
{
using (VideoFileWriter vFWriter = new VideoFileWriter())
{
//Create new video file:
vFWriter.Open(outputPath + "//" + videoName, width, height, frameRate, VideoCodec.MPEG4);

//Make each screenshot into a video frame:
foreach (string imageLocation in inputImageSequence)
{
Bitmap imageFrame = System.Drawing.Image.FromFile(imageLocation) as Bitmap;
vFWriter.WriteVideoFrame(imageFrame);
imageFrame.Dispose();
}

//Close:
vFWriter.Close();
}
}

//Combine video and audio files:
private void CombineVideoAndAudio(string video, string audio)
{
//FFMPEG command to combine video and audio:
string args = $"/c ffmpeg -i "{video}" -i "{audio}" -shortest {finalName}";
ProcessStartInfo startInfo = new ProcessStartInfo
{
CreateNoWindow = false,
FileName = "cmd.exe",
WorkingDirectory = outputPath,
Arguments = args
};

//Execute command:
using (Process exeProcess = Process.Start(startInfo))
{
exeProcess.WaitForExit();
}
}

public void Stop()
{
//Stop watch:
watch.Stop();

//Video variables:
int width = bounds.Width;
int height = bounds.Height;
int frameRate = 10;

//Save audio:
SaveAudio();

//Save video:
SaveVideo(width, height, frameRate);

//Combine audio and video files:
CombineVideoAndAudio(videoName, audioName);

//Delete the screenshots and temporary folder:
DeletePath(tempPath);

//Delete separated video and audio files:
DeleteFilesExcept(outputPath, outputPath + "\" + finalName);
}
}
}