C# – choose a custom image for C# Windows Application Drag Drop functions

cdrag and dropwinforms

I am writing a small project where I would like to make use of drag and drop functionalty to ease some of the operations for the end user. To make the application a little more appealing, I would like to display the object being dragged. I have found some resources with WPF, but I don't know any WPF, so it becomes a bit tough to bite down on that whole subject for this single task. I would like to know how this can be done with "regular" C# Windows Forms. So far, all drag drop tutorials I've found just talk about the drop effects which is just a preset of a few icons.

WPF sounds like something I want to learn after this project.

Best Answer

The blog link provided by @Jesper gives the two or three key nuggets of info, but I think it is worth bringing it into S.O. for posterity.

Set up the custom cursor

The code below allows you to use an arbitrary image for your cursor

 public struct IconInfo
  {
    public bool fIcon;
    public int xHotspot;
    public int yHotspot;
    public IntPtr hbmMask;
    public IntPtr hbmColor;
  }

    [DllImport("user32.dll")]
    public static extern IntPtr CreateIconIndirect(ref IconInfo icon);

    [DllImport("user32.dll")]
    [return: MarshalAs(UnmanagedType.Bool)]
    public static extern bool GetIconInfo(IntPtr hIcon, ref IconInfo pIconInfo);

    public static Cursor CreateCursor(Bitmap bmp, int xHotSpot, int yHotSpot)
    {
      IconInfo tmp = new IconInfo();
      GetIconInfo(bmp.GetHicon(), ref tmp);
      tmp.xHotspot = xHotSpot;
      tmp.yHotspot = yHotSpot;
      tmp.fIcon = false;
      return new Cursor(CreateIconIndirect(ref tmp));
    }

Set up the drag and drop event handling

This is well covered in other tutorials and answers. The specific events we are concerned about here are GiveFeedback and DragEnter, on any control where you want the custom cursor to apply.

 private void DragSource_GiveFeedback(object sender, GiveFeedbackEventArgs e)
    {
      e.UseDefaultCursors = 0;
    }

   private void DragDest_DragEnter(object sender, DragEventArgs e)
    {

      Cursor.Current = CreateCursor(bitmap, 0, 0);
     }

Related Solutions

C# – How to drag and drop files into an application

Some sample code:

  public partial class Form1 : Form {
    public Form1() {
      InitializeComponent();
      this.AllowDrop = true;
      this.DragEnter += new DragEventHandler(Form1_DragEnter);
      this.DragDrop += new DragEventHandler(Form1_DragDrop);
    }

    void Form1_DragEnter(object sender, DragEventArgs e) {
      if (e.Data.GetDataPresent(DataFormats.FileDrop)) e.Effect = DragDropEffects.Copy;
    }

    void Form1_DragDrop(object sender, DragEventArgs e) {
      string[] files = (string[])e.Data.GetData(DataFormats.FileDrop);
      foreach (string file in files) Console.WriteLine(file);
    }
  }

C# – How to save application settings in a Windows Forms application

If you work with Visual Studio then it is pretty easy to get persistable settings. Right click on the project in Solution Explorer and choose Properties. Select the Settings tab and click on the hyperlink if settings doesn't exist.

Use the Settings tab to create application settings. Visual Studio creates the files Settings.settings and Settings.Designer.settings that contain the singleton class Settings inherited from ApplicationSettingsBase. You can access this class from your code to read/write application settings:

Properties.Settings.Default["SomeProperty"] = "Some Value";
Properties.Settings.Default.Save(); // Saves settings in application configuration file

This technique is applicable both for console, Windows Forms, and other project types.

Note that you need to set the scope property of your settings. If you select Application scope then Settings.Default.<your property> will be read-only.

Reference: How To: Write User Settings at Run Time with C# - Microsoft Docs