[C#/WINFORM] Form 클래스 : 마우스로 폼 이동시키기

using System.Drawing;
using System.Windows.Forms;

/// <summary>
/// 테스트 폼
/// </summary>
public partial class TestForm : Form
{
    //////////////////////////////////////////////////////////////////////////////////////////////////// Field
    ////////////////////////////////////////////////////////////////////////////////////////// Private

    #region Field

    /// <summary>
    /// 드래그 여부
    /// </summary>
    private bool isDragging;

    /// <summary>
    /// 시작 위치
    /// </summary>
    private Point startPoint;

    #endregion

    //////////////////////////////////////////////////////////////////////////////////////////////////// Constructor
    ////////////////////////////////////////////////////////////////////////////////////////// Public

    #region 생성자 - TestForm()

    /// <summary>
    /// 생성자
    /// </summary>
    public TestForm()
    {
        InitializeComponent();

        MouseDown += Form_MouseDown;
        MouseMove += Form_MouseMove;
        MouseUp   += Form_MouseUp;
    }

    #endregion

    //////////////////////////////////////////////////////////////////////////////////////////////////// Method
    ////////////////////////////////////////////////////////////////////////////////////////// Private
    //////////////////////////////////////////////////////////////////////////////// Event

    #region 폼 마우스 다운시 처리하기 - Form_MouseDown(sender, e)

    /// <summary>
    /// 폼 마우스 다운시 처리하기
    /// </summary>
    /// <param name="sender">이벤트 발생자</param>
    /// <param name="e">이벤트 인자</param>
    private void Form_MouseDown(object sender, MouseEventArgs e)
    {
        this.startPoint.X = e.X;
        this.startPoint.Y = e.Y;

        this.isDragging = true;
    }

    #endregion

    #region 폼 마우스 이동시 처리하기 - Form_MouseMove(sender, e)

    /// <summary>
    /// 폼 마우스 이동시 처리하기
    /// </summary>
    /// <param name="sender">이벤트 발생자</param>
    /// <param name="e">이벤트 인자</param>
    private void Form_MouseMove(object sender, MouseEventArgs e)
    {
        if(this.isDragging)
        {
            Point screenPoint = PointToScreen(e.Location);

            Location = new Point
            (
                screenPoint.X - this.startPoint.X,
                screenPoint.Y - this.startPoint.Y
            );
        }
    }

    #endregion

    #region 폼 마우스 업시 처리하기 - Form_MouseUp(sender, e)

    /// <summary>
    /// 폼 마우스 업시 처리하기
    /// </summary>
    /// <param name="sender">이벤트 발생자</param>
    /// <param name="e">이벤트 인자</param>
    private void Form_MouseUp(object sender, MouseEventArgs e)
    {
        this.isDragging = false;
    }

    #endregion
}