using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;
using YoutubeExplode;
using YoutubeExplode.Videos.Streams;

namespace YouTubeDownloader
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private async void btnDownload_Click(object sender, EventArgs e)
        {
            string[] videoUrls = txtUrls.Text.Split(new[] { "\r\n", "\r", "\n" }, StringSplitOptions.RemoveEmptyEntries);

            if (videoUrls.Length == 0)
            {
                MessageBox.Show("Please enter at least one YouTube video URL.");
                return;
            }

            // Disable the download button while downloading
            btnDownload.Enabled = false;
            lblStatus.Text = "Status: Downloading...";

            var youtube = new YoutubeClient();
            var tasks = new List<Task>();

            progressBar.Maximum = videoUrls.Length;
            progressBar.Value = 0;

            foreach (var videoUrl in videoUrls)
            {
                tasks.Add(Task.Run(async () =>
                {
                    try
                    {
                        var video = await youtube.Videos.GetAsync(videoUrl);
                        var streamManifest = await youtube.Videos.Streams.GetManifestAsync(video.Id);
                        var streamInfo = streamManifest.GetMuxedStreams().GetWithHighestVideoQuality();

                        if (streamInfo != null)
                        {
                            var saveFileDialog = new SaveFileDialog
                            {
                                FileName = $"{video.Title}.mp4",
                                Filter = "MP4 Files|*.mp4"
                            };

                            if (InvokeRequired)
                            {
                                Invoke(new Action(() => saveFileDialog.ShowDialog()));
                            }
                            else
                            {
                                saveFileDialog.ShowDialog();
                            }

                            var filePath = saveFileDialog.FileName;

                            if (!string.IsNullOrWhiteSpace(filePath))
                            {
                                await youtube.Videos.Streams.DownloadAsync(streamInfo, filePath);
                            }
                        }
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show($"An error occurred while downloading a video: {ex.Message}");
                    }
                    finally
                    {
                        Invoke(new Action(() => progressBar.Value++));
                    }
                }));
            }

            await Task.WhenAll(tasks);

            btnDownload.Enabled = true;
            lblStatus.Text = "Status: Waiting";
            progressBar.Value = 0;

            MessageBox.Show("All videos have been downloaded.");
        }
    }
}

C Sharp Online Compiler

Write, Run & Share C# code online using OneCompiler's C# online compiler for free. It's one of the robust, feature-rich online compilers for C# language, running on the latest version 8.0. Getting started with the OneCompiler's C# compiler is simple and pretty fast. The editor shows sample boilerplate code when you choose language as C# and start coding.

Read inputs from stdin

OneCompiler's C# online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

using System;
 
namespace Sample
{
  class Test
    {
      public static void Main(string[] args)
       {
         string name;
         name = Console.ReadLine();
         Console.WriteLine("Hello {0} ", name);
	}
     }
}

About C Sharp

C# is a general purpose object-oriented programming language by Microsoft. Though initially it was developed as part of .net but later it was approved by ECMA and ISO standards.

You can use C# to create variety of applications, like web, windows, mobile, console applications and much more using Visual studio.

Syntax help

Data types

Data TypeDescriptionRangesize
intTo store integers-2,147,483,648 to 2,147,483,6474 bytes
doubleto store large floating point numbers with decimalscan store 15 decimal digits8 bytes
floatto store floating point numbers with decimalscan store upto 7 decimal digits4 bytes
charto store single characters-2 bytes
stringto stores text-2 bytes per character
boolto stores either true or false-1 bit

Variables

Syntax

datatype variable-name = value;

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition or set of few conditions IF-ELSE is used.

if(conditional-expression) {
   // code
} 
else {
   // code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement) {
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

data-type[] array-name;

Methods

Method is a set of statements which gets executed only when they are called. Call the method name in the main function to execute the method.

Syntax

static void method-name() 
{
  // code to be executed
}