C#

α.γεεκ

Fortune passes everywhere.
Duke Leto Atreides

private void Form1_Load(object sender, System.EventArgs e)
{
    //This is vital - tells the picturebox to accept dragdrop notifications
    //For some reason it does not seem to appear in intellisense or the Visual Studio designer.
    //It does build though!!
    this.pictureBox1.AllowDrop = true;
}

private void pictureBox1_DragEnter(object sender, System.Windows.Forms.DragEventArgs e)
{
    //Make sure item being dropped is a file
    if (e.Data.GetDataPresent(DataFormats.FileDrop))
    {
        e.Effect = DragDropEffects.All;
    }
    else//Otherwise do not allow drop
    {
        e.Effect = DragDropEffects.None;
    }
}

private void pictureBox1_DragDrop(object sender, System.Windows.Forms.DragEventArgs e)
{
    //Get an array of strings - needs an array because the user can drag more than one item
    //into the picturebox
    string[] itemsInDrop = (string[])e.Data.GetData("FileDrop", false);

    //loop over the strings
    foreach (string path in itemsInDrop)
    {
        //Do what you want here.
        //I check the iamge exists then try to load it into the picturebox.
        //This is obviously a bit pointless for more than one image, but acts as an example.
        //NB System.ArgumentException is thrown when you try to instantiate a bitmap object
        //with an invalid file path.
        FileInfo CheckForImage = new FileInfo(path);

        if(!CheckForImage.Exists)
        {return;}

        try
        {
            Bitmap newImage = new Bitmap(path);
            this.pictureBox1.Image = newImage;
        }
        catch(System.ArgumentException)
        {
            MessageBox.Show("The file at " + path + " is not a valid image.", "Invalid Image", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }
}