Get Picturebox File Name

1: You have to make sure the file is an image
2: You need to show images one at a time
3: You already have filename in array

    public partial class Form1 : Form
    {
        PictureBox pbx;     
        string[] files;
       int index = 0;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            loadPicboxFiles();
        }

        public void loadPicboxFiles()
        {
            pbx = new PictureBox();
            pbx.Name = "pic1";
            pbx.SizeMode = PictureBoxSizeMode.AutoSize;
            pbx.Left = 10;
            pbx.Top = 10;
            pbx.DoubleClick += new EventHandler(pbx_DoubleClick);

            this.Controls.Add(pbx);
            files = Directory.GetFiles(@"D:\Building_Case");
        }

        private void button1_Click(object sender, EventArgs e)
        {        
        
          
                if (checkFileIsImage(files[index]))
                {
                    pbx.Image = Image.FromFile(files[index]);
                    textBox1.Text = files[index];
                    Application.DoEvents();
                
                    System.Threading.Thread.Sleep(2000);
                  
                }

                index++;
        }

        public bool checkFileIsImage(string _file)
        {
            bool isImage = false;
            string str = Path.GetExtension(_file);
            if(str == ".jpg" |str ==".png"|str ==".bmp")
            {
                isImage = true;
            }                      
            return isImage;
        }
    

        private void  pbx_DoubleClick(object sender, EventArgs e)
        {
            MessageBox.Show(files[index]);
        }
    }