将图像从 PictureBox 拖放到另一个 PictureBox 并检查目标 PictureBox 是否正确

Question

I'm new to programming. I'm making an application for first-grade kids in Visual Studio 2019 WindowsForm and one level is about dragging a picture from a PictureBox in an empty PictureBox that has a label with a simple definition.

So if I have 2 PictureBox that show let say a dog and a chicken and 2 empty PictureBox (1 with label "bones" and one with label "grain"). I want to drag the dog picture into the PictureBox with the label "bones" and the chicken in the one with "grain" label and if correct I show a text "great job" and if not I show a text "try again".

I can drag the pictures but I can't find a method to check if is correct. Can anybody help me with that?

Here is my code so far:

    private void NivelulDoi_Load(object sender, EventArgs e)
        {
            customPictureBox1.AllowDrop = true;
            customPictureBox2.AllowDrop = true;
            customPictureBox3.AllowDrop = true;
        }

        private void customPictureBox1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                customPictureBox1.DoDragDrop(customPictureBox1.Image, DragDropEffects.Copy);
            }
        }

        private void customPictureBox1_DragDrop(object sender, DragEventArgs e)
        {
            var data = e.Data.GetData(DataFormats.FileDrop);
            if (data != null)
            {
                var fileNames = data as string[];
                if (fileNames.Length > 0)
                {
                    customPictureBox1.Image = Image.FromFile(fileNames[0]);
                }
            }
        }

        private void customPictureBox1_DragEnter(object sender, DragEventArgs e)
        {
            e.Effect = DragDropEffects.Copy;
        }

        private void customPictureBox2_DragEnter(object sender, DragEventArgs e)
        {
            Dragging(e);
        }

        private void customPictureBox2_DragDrop(object sender, DragEventArgs e)
        {
            customPictureBox2.Image = (Bitmap)e.Data.GetData(DataFormats.Bitmap, true);
            
            // figure out how to check if correct 
            /*if (customPictureBox2.Image == (Bitmap)e.Data.GetData(DataFormats.Bitmap, true))
            {
                label1.Text = "ai reusit";
            }
            else
            {
                label1.Text = "mai incearca";
            }*/   
        }

        private void customPictureBox3_DragEnter(object sender, DragEventArgs e)
        {
            Dragging(e);
        }

        private void customPictureBox3_DragDrop(object sender, DragEventArgs e)
        {
            customPictureBox3.Image = (Bitmap)e.Data.GetData(DataFormats.Bitmap, true);
        }

        private void customPictureBox4_DragEnter(object sender, DragEventArgs e)
        {
            Dragging(e);
        }

        private void customPictureBox4_DragDrop(object sender, DragEventArgs e)
        {
            customPictureBox4.Image = (Bitmap)e.Data.GetData(DataFormats.Bitmap, true);
        }

        private static void Dragging(DragEventArgs e)
        {
            if (e.Data.GetDataPresent(DataFormats.Bitmap) && (e.AllowedEffect & DragDropEffects.Copy) != 0)
            {
                e.Effect = DragDropEffects.Copy;
            }
            else
            {
                e.Effect = DragDropEffects.None;
            }
        }
    }
}

Thank you.

Answer 1

A simple way is to define a variable to save the Name of "picturebox drag" and a dictionary to save "drag-drop" pair.

Here is the demo.

string pictureBoxFrom = "";
Dictionary<string, string> picDict = new Dictionary<string, string>();
public Form1()
{
    InitializeComponent();
    pictureBox2.AllowDrop = true;
    pictureBox4.AllowDrop = true;
    pictureBox1.MouseDown += pictureBox_MouseDown;
    pictureBox3.MouseDown += pictureBox_MouseDown;
    pictureBox2.DragEnter += pictureBox_DragEnter;
    pictureBox2.DragDrop += pictureBox_DragDrop;
    pictureBox4.DragEnter += pictureBox_DragEnter;
    pictureBox4.DragDrop += pictureBox_DragDrop;

    picDict.Add("pictureBox1", "pictureBox2"); // drag 1 to 2
    picDict.Add("pictureBox3", "pictureBox4"); // drag 3 to 4
}

private void pictureBox_MouseDown(object sender, MouseEventArgs e)
{
    pictureBoxFrom = (sender as PictureBox).Name;
    var img = (sender as PictureBox).Image;
    if (img == null) return;
    if (DoDragDrop(img, DragDropEffects.Move) == DragDropEffects.Move)
    {
        //(sender as PictureBox).Image = null;
    }
}

private void pictureBox_DragEnter(object sender, DragEventArgs e)
{
    if (e.Data.GetDataPresent(DataFormats.Bitmap))
        e.Effect = DragDropEffects.Move;
}

private void pictureBox_DragDrop(object sender, DragEventArgs e)
{
    if (picDict.ContainsKey(pictureBoxFrom) && picDict[pictureBoxFrom].Equals((sender as PictureBox).Name))
    {
        var bmp = (Bitmap)e.Data.GetData(DataFormats.Bitmap);
        (sender as PictureBox).Image = bmp;
        MessageBox.Show("great job");
    }
    else
    {
        MessageBox.Show("try again");
    }
}