C#

C#:
namespace LISTBOX_fareileSURUKLEbirakDRAGDROP_Olaylari
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            
            listBox1.AllowDrop = true;
            listBox2.AllowDrop = true;

            int i;
            for(i = 0; i < 10; i++)
            {
                listBox1.Items.Add(i);
            }
        }

        private void listBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (listBox1.Items.Count == 0) return;

            string deger = listBox1.Items[listBox1.IndexFromPoint(e.X,e.Y)].ToString();

            if (DoDragDrop(deger, DragDropEffects.All) == DragDropEffects.All)
                listBox1.Items.RemoveAt(listBox1.IndexFromPoint(e.X, e.Y));
        }
        private void listBox2_DragOver(object sender,DragEventArgs e)
        {
            e.Effect= DragDropEffects.All;
        }
        private void listBox2_DragDrop(object sender, DragEventArgs e)
        {
            if (e.Data.GetDataPresent(DataFormats.StringFormat))
                listBox2.Items.Add(e.Data.GetData(DataFormats.StringFormat));
        }
    }
}

This simple code gives Exception Handling Error:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Label_LinkLabel_TextboxKONTROLLERI
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        LinkLabel dynamicLinkLabel = new LinkLabel();
        private void Form2_Load(object sender, EventArgs e)
        {
            dynamicLinkLabel.BackColor = Color.Red;
            dynamicLinkLabel.ForeColor = Color.Blue;
            dynamicLinkLabel.Text = "I am a Dynamic LinkLabel";
            dynamicLinkLabel.TextAlign = (ContentAlignment)HorizontalAlignment.Center;
            dynamicLinkLabel.Text += " Appended text";
            dynamicLinkLabel.Name = "DynamicLinkLabel";
            dynamicLinkLabel.Font = new Font("Georgia", 16);
            Controls.Add(dynamicLinkLabel);
            dynamicLinkLabel.Name = "DynamicLinkLabel";
            string name = dynamicLinkLabel.Name;
            dynamicLinkLabel.Location = new Point(20, 150);
            dynamicLinkLabel.Height = 40;
            dynamicLinkLabel.Width = 300;
            dynamicLinkLabel.BackColor = Color.Red;
            dynamicLinkLabel.ForeColor = Color.Blue;
            dynamicLinkLabel.BorderStyle = BorderStyle.FixedSingle;

            dynamicLinkLabel.ActiveLinkColor = Color.Orange;
            dynamicLinkLabel.VisitedLinkColor = Color.Green;
            dynamicLinkLabel.LinkColor = Color.RoyalBlue;
            dynamicLinkLabel.DisabledLinkColor = Color.Gray;

            dynamicLinkLabel.LinkArea = new LinkArea(0, 22);
            dynamicLinkLabel.Links.Add(24, 9, "http://www.c-sharpcorner.com");
            dynamicLinkLabel.LinkClicked += new LinkLabelLinkClickedEventHandler(LinkedLabelClicked);
        }
        private void LinkedLabelClicked(object sender, LinkLabelLinkClickedEventArgs e)
        {
            dynamicLinkLabel.LinkVisited = true;
            System.Diagnostics.Process.Start("http://www.c-sharpcorner.com");
        }
    }
}
The code above has been taken from this website: https://www.c-sharpcorner.com/UploadFile/mahesh/linklabel-in-C-Sharp/

Here is the exception:
System.ComponentModel.Win32Exception: 'An error occurred trying to start process 'http://www.c-sharpcorner.com' with working directory 'C:\Users\LENOVO\Desktop\Murat Yücedağ Projeler\Label_LinkLabel_TextboxKONTROLLERI\Label_LinkLabel_TextboxKONTROLLERI\bin\Debug\net6.0-windows'. The system cannot find the file specified.'


Here is the CS8604 Warning:  https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/nullable-warnings?f1url=%3FappId%3Droslyn%26k%3Dk(CS8604)

I did not understand what causes this. How can I solve this problem?

var products = _context.Products.ToList();

var products = await _context.Products.ToListAsync();