How to disable the minimize button in C#?

Question

In my application I need to temporarily gray out the minimize button of the main form. Any ideas how this can be achieved? I don't mind doing p/invokes to Win32 dlls.

Edit: Graying out the minimize button would be the preferred solution, but is there any other way of preventing the form from becoming minimized?

Answer 1

I read your comment in regards to my response and was able to drum up a more complete solution for you. I ran this quickly and it seemed to have the behavior that you wanted. Instead of deriving your winforms from Form, derive from this class:

using System;
using System.Windows.Forms;
using System.ComponentModel;

namespace NoMinimizeTest
{
    public class MinimizeControlForm : Form
    {
        private const int WM_SYSCOMMAND = 0x0112;
        private const int SC_MINIMIZE = 0xf020;

        protected MinimizeControlForm()
        {
            AllowMinimize = true;
        }

        protected override void WndProc(ref Message m)
        {
            if (!AllowMinimize)
            {
                if (m.Msg == WM_SYSCOMMAND)
                {
                    if (m.WParam.ToInt32() == SC_MINIMIZE)
                    {
                        m.Result = IntPtr.Zero;
                        return;
                    }
                }
            }
            base.WndProc(ref m);
        }

        [Browsable(true)]
        [Category("Behavior")]
        [Description("Specifies whether to allow the window to minimize when the minimize button and command are enabled.")]
        [DefaultValue(true)]
        public bool AllowMinimize
        {
            get;
            set;
        }
    }
}

You could do a bit more if you wanted to be able to decide whether to allow minimizing at the time the click is sent, for instance:

using System;
using System.Windows.Forms;
using System.ComponentModel;

namespace NoMinimizeTest
{
    public class MinimizeControlForm : Form
    {
        private const int WM_SYSCOMMAND = 0x0112;
        private const int SC_MINIMIZE = 0xf020;

        protected MinimizeControlForm()
        {

        }

        protected override void WndProc(ref Message m)
        {
            if (m.Msg == WM_SYSCOMMAND)
            {
                if (m.WParam.ToInt32() == SC_MINIMIZE && !CheckMinimizingAllowed())
                {
                    m.Result = IntPtr.Zero;
                    return;
                }
            }
            base.WndProc(ref m);
        }

        private bool CheckMinimizingAllowed()
        {
            CancelEventArgs args = new CancelEventArgs(false);
            OnMinimizing(args);
            return !args.Cancel;
        }

        [Browsable(true)]
        [Category("Behavior")]
        [Description("Allows a listener to prevent a window from being minimized.")]
        public event CancelEventHandler Minimizing;

        protected virtual void OnMinimizing(CancelEventArgs e)
        {
            if (Minimizing != null)
                Minimizing(this, e);
        }
    }
}

For more information about this window notification, see the MSDN article about it.