using System;

using System.Collections.Generic;

using System.Text;

using System.Threading;

using System.Windows.Forms;

using System.Drawing;

using System.Diagnostics;

namespace AnimatedTransform

{

    static class FormTransform

    {

        public static void TransformSize(Form frm, int newWidth, int newHeight)

        {

            TransformSize(frm, new Size(newWidth, newHeight));

        }

        public static void TransformSize(Form frm, Size newSize)

        {

            ParameterizedThreadStart threadStart = new ParameterizedThreadStart(RunTransformation);

            Thread transformThread = new Thread(threadStart);

            transformThread.Start(new object[] { frm, newSize });

        }

        private delegate void RunTransformationDelegate(object paramaters);

        private static void RunTransformation(object parameters)

        {

            Form frm = (Form)((object[])parameters)[0];

            if (frm.InvokeRequired)

            {

                RunTransformationDelegate del = new RunTransformationDelegate(RunTransformation);

                frm.Invoke(del, parameters);

            }

            else

            {

                //动画的变量參数

                double FPS = 300.0;

                long interval = (long)(Stopwatch.Frequency / FPS);

                long ticks1 = 0;

                long ticks2 = 0;

                //传进来的新的窗口的大小

                Size size = (Size)((object[])parameters)[1];

                int xDiff = Math.Abs(frm.Width - size.Width);

                int yDiff = Math.Abs(frm.Height - size.Height);

                int step = 10;

                int xDirection = frm.Width < size.Width ? 1 : -1;

                int yDirection = frm.Height < size.Height ?

1 : -1;

                int xStep = step * xDirection;

                int yStep = step * yDirection;

                //要调整的窗口的宽度是否在步长之内

                bool widthOff = IsWidthOff(frm.Width, size.Width, xStep);

                //要调整的窗口的高度是否在步长之内

                bool heightOff = IsHeightOff(frm.Height, size.Height, yStep);

                while (widthOff || heightOff)

                {

                    //获取当前的时间戳

                    ticks2 = Stopwatch.GetTimestamp();

                    //同意调整大小仅在有足够的时间来刷新窗口的时候

                    if (ticks2 >= ticks1 + interval)

                    {

                        //调整窗口的大小

                        if (widthOff)

                            frm.Width += xStep;

                        if (heightOff)

                            frm.Height += yStep;

                        widthOff = IsWidthOff(frm.Width, size.Width, xStep);

                        heightOff = IsHeightOff(frm.Height, size.Height, yStep);

                        //同意窗口刷新

                        Application.DoEvents();

                        //保存当前的时间戳

                        ticks1 = Stopwatch.GetTimestamp();

                    }

                    Thread.Sleep(1);

                }

            }

        }

        private static bool IsWidthOff(int currentWidth, int targetWidth, int step)

        {

            //目标宽度与当前宽度是否在步长之内，假设是，返回false

            if (Math.Abs(currentWidth - targetWidth) <= Math.Abs(step)) return false;

            return (step > 0 && currentWidth < targetWidth) ||

                   (step < 0 && currentWidth > targetWidth);

        }

        private static bool IsHeightOff(int currentHeight, int targetHeight, int step)

        {

            //目标高度与当前高度是否在步长之内，假设是，返回false

            if (Math.Abs(currentHeight - targetHeight) <= Math.Abs(step)) return false;

            return (step > 0 && currentHeight < targetHeight) ||

                   (step < 0 && currentHeight > targetHeight);

        }

    }

}

调用方法：

Random random = new Random();

            int width = random.Next(100, 500);//随机数产生窗口的宽

            int height = random.Next(50, 800);//随机数产生窗口的高

            FormTransform.TransformSize(this, width, height);