A C# class used to control fading forms in and out

Fader.cs

using System;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace FormFader
{
    /// <summary>
    /// An object used to control fading forms in and out.
    /// </summary>
    class Fader
    {
        // This delegate is later used as a call back for
        // when the form has completed fading.
        public delegate void FadeCompleted();

        // Class properties
        private readonly Form form;                                           // The form to modify the opacity of.
        private readonly Form parentForm;                                     // The parent form if being displayed as a dialog.
        private FadeDirection fadeDirection;                                  // The direction in which to fade.
        private float fadeSpeed;                                              // The speed at which to fade.
        private FadeCompleted fadeFinished;                                   // The delegate to call when a fade has completed.
        private bool shouldClose;                                             // If set to true, the form will close after fading out.
        private readonly TaskCompletionSource<DialogResult> showDialogResult  // The Async Task Completion Source for displaying as a dialog.
            = new TaskCompletionSource<DialogResult>();

        // Enum for controlling the fade direction.
        private enum FadeDirection
        {
            In,
            Out
        }

        // Constants for setting the fade speed. 
        // (You can alternately use a custom float value)
        public static class FadeSpeed
        {
            public static readonly float Slowest = 1;
            public static readonly float Slower = 10;
            public static readonly float Slow = 25;
            public static readonly float Normal = 50;
            public static readonly float Fast = 60;
            public static readonly float Faster = 75;
            public static readonly float Fastest = 100;
        }

        /// <summary>
        /// Construct the Fader object with a form.
        /// </summary>
        private Fader(Form form)
        {
            this.form = form;
        }

        /// <summary>
        /// Construct a Fader object with a form and a parent form.
        /// </summary>
        private Fader(Form form, Form parent) : this(form)
        {
            this.parentForm = parent;
        }

        /// <summary>
        /// Begin fading the form.
        /// </summary>
        private void BeginFade()
        {
            UpdateOpacity();
            fadeFinished?.Invoke();
        }

        /// <summary>
        /// Update the opacity of the form using the timer.
        /// </summary>
        private async void UpdateOpacity()
        {
            if (form.IsDisposed)
            {
                return;
            }

            switch (fadeDirection)
            {
                // Fade in
                case FadeDirection.In:
                    if (form.Opacity < 1.0)
                        form.Opacity += (fadeSpeed / 1000.0);
                    else
                        return;

                    break;

                // Fade out
                case FadeDirection.Out:
                    if (form.Opacity > 0.1)
                    {
                        form.Opacity -= (fadeSpeed / 1000.0);
                    }
                    else
                    {
                        if (!shouldClose)
                            form.Hide();
                        else
                            form.Close();

                        return;
                    }
                    break;
            }

            await Task.Delay(10);
            UpdateOpacity();
        }

        /// <summary>
        /// Fade the form in at the defined speed as a dialog
        /// based on parent form.
        /// </summary>
        private async Task<DialogResult> ShowDialog(float fadeSpeed, FadeCompleted finished)
        {
            parentForm.BeginInvoke(new Action(() => showDialogResult.SetResult(form.ShowDialog(parentForm))));
            
            fadeFinished = finished;
            form.Opacity = 0;
            this.fadeSpeed = fadeSpeed;
            fadeDirection = FadeDirection.In;
            BeginFade();

            return await showDialogResult.Task;
        }

        /// <summary>
        /// Fade the form in at the defined speed.
        /// </summary>
        private void FadeIn(float fadeSpeed, FadeCompleted finished)
        {
            form.Opacity = 0;
            form.Show();

            fadeFinished = finished;
            this.fadeSpeed = fadeSpeed;
            fadeDirection = FadeDirection.In;

            BeginFade();
        }

        /// <summary>
        /// Fade the form out at the defined speed.
        /// </summary>
        private void FadeOut(float fadeSpeed, FadeCompleted finished)
        {
            if (form.Opacity < 0.1)
            {
                finished?.Invoke();
                return;
            }

            fadeFinished = finished;
            form.Opacity = 100;
            this.fadeSpeed = fadeSpeed;
            fadeDirection = FadeDirection.Out;

            BeginFade();
        }

        /// <summary>
        /// Fades a dialog in using parent form and defined fade speed.
        /// </summary>
        public async static Task<DialogResult> ShowDialog(Form form, Form parent, float fadeSpeed)
        {
            Fader fader = new Fader(form, parent);
            return await fader.ShowDialog(fadeSpeed, null);
        }

        /// <summary>
        /// Fades a dialog in using parent form and defined fade speed
        /// and call the finished delegate.)
        /// </summary>
        public async static Task<DialogResult> ShowDialog(Form form, Form parent, float fadeSpeed, FadeCompleted finished)
        {
            Fader fader = new Fader(form, parent);
            return await fader.ShowDialog(fadeSpeed, finished);
        }

        /// <summary>
        /// Fade a form in at the defined speed.
        /// </summary>
        public static void FadeIn(Form form, float fadeSpeed, FadeCompleted finished)
        {
            Fader fader = new Fader(form);
            fader.FadeIn(fadeSpeed, finished);
        }

        /// <summary>
        /// Fade a form out at the defined speed.
        /// </summary>
        public static void FadeOut(Form form, float fadeSpeed, FadeCompleted finished)
        {
            Fader fader = new Fader(form);
            fader.FadeOut(fadeSpeed, finished);
        }

        /// <summary>
        /// Fade a form in at the defined speed.
        /// </summary>
        public static void FadeIn(Form form, float fadeSpeed)
        {
            Fader fader = new Fader(form);
            fader.FadeIn(fadeSpeed, null);
        }

        /// <summary>
        /// Fade a form out at the defined speed.
        /// </summary>
        public static void FadeOut(Form form, float fadeSpeed)
        {
            Fader fader = new Fader(form);
            fader.FadeOut(fadeSpeed, null);
        }

        /// <summary>
        /// Fade a form out at the defined speed and
        /// close it when the fade has completed.
        /// </summary>
        public static void FadeOutAndClose(Form form, float fadeSpeed)
        {
            Fader fader = new Fader(form)
            {
                shouldClose = true
            };
            fader.FadeOut(fadeSpeed, null);
        }

        /// <summary>
        /// Fade a form out at the defined speed and
        /// close it when the fade has completed.
        /// After the form has closed, call the FadeComplete delegate.
        /// </summary>
        public static void FadeOutAndClose(Form form, float fadeSpeed, FadeCompleted finished)
        {
            Fader fader = new Fader(form)
            {
                shouldClose = true
            };
            fader.FadeOut(fadeSpeed, finished);
        }
    }
}

Great library!! However, seems showdialog does not apply fadeIn feature?

Great library!! However, seems showdialog does not apply fadeIn feature?

Are you using the ShowDialog from within this class? In my testing it fades it in just fine. Can you give an example?

Awesome library!

Hello and thanks for the library. I have tried to show a ShowDialog with the effect, but I can not do it. This is my code:

private void btnFinal_Click(object sender, EventArgs e)
{
    var frm = new DlgNumeration();
    frm.Visible = false;
    Fader.ShowDialog(frm, this, Fader.FadeSpeed.Slower);
}

Hello and thanks for the library. I have tried to show a ShowDialog with the effect, but I can not do it. This is my code:

private void btnFinal_Click(object sender, EventArgs e)
{
    var frm = new DlgNumeration();
    frm.Visible = false;
    Fader.ShowDialog(frm, this, Fader.FadeSpeed.Slower);
}

Try removing frm.Visible = false; and see if that works.

Hello and thanks for the library. I have tried to show a ShowDialog with the effect, but I can not do it. This is my code:

private void btnFinal_Click(object sender, EventArgs e)
{
    var frm = new DlgNumeration();
    frm.Visible = false;
    Fader.ShowDialog(frm, this, Fader.FadeSpeed.Slower);
}

Try removing frm.Visible = false; and see if that works.

Hi, I've done that but it does not work, it shows the form but without the effect.

Hello and thanks for the library. I have tried to show a ShowDialog with the effect, but I can not do it. This is my code:

private void btnFinal_Click(object sender, EventArgs e)
{
    var frm = new DlgNumeration();
    frm.Visible = false;
    Fader.ShowDialog(frm, this, Fader.FadeSpeed.Slower);
}

Try removing frm.Visible = false; and see if that works.

Hi, I've done that but it does not work, it shows the form but without the effect.

Check the latest update, i believe it fixes this issue!

Thanks for this.

Thank you for this code, Nate. I used it the other day to solve a little challenge I had. It worked like a champ! https://github.com/rogerpence/toast-notifications-for-windows

Thank you for this code, Nate. I used it the other day to solve a little challenge I had. It worked like a champ! https://github.com/rogerpence/toast-notifications-for-windows

Glad it helped! Feel free to give the snippet a star if you're feeling so inclined :)