在WinForm程序中，要移动没有标题栏的窗口，基本的实现思路是监听需要拖动窗口内的控件的鼠标事件，然后将鼠标位置发送给窗口进行相应的位移就可以了。通过借用Windows API也可以很容易实现这一点，比如像下面这样。

public class Win32Api
{
    public const int WM_SYSCOMMAND = 0x112;
    public const int SC_DRAGMOVE = 0xF012;

    [DllImport("user32.Dll", EntryPoint = "ReleaseCapture")]
    public extern static void ReleaseCapture(); // 鼠标捕获
    [DllImport("user32.Dll", EntryPoint = "SendMessage")]
    public extern static void SendMessage(IntPtr hWnd, int wMsg, int wParam, int lParam); // 将消息发送给指定的窗口
}

private void pnlHeader_MouseDown(object sender, MouseEventArgs e)
{
    Win32Api.ReleaseCapture();
    Win32Api.SendMessage(this.Handle, Win32Api.WM_SYSCOMMAND, Win32Api.SC_DRAGMOVE, 0);
}

当然，你还可以向这样向窗口发送消息，来实现拖动自定义标题栏移动窗口

public const int WM_NCLBUTTONDOWN = 0x00A1;
public const int HTCAPTION = 2;

private void pnlHeader_MouseDown(object sender, MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        // 释放控件已捕获的鼠标
        pnlHeader.Capture = false;

        // 创建并发送WM_NCLBUTTONDOWN消息
        Message msg =
            Message.Create(this.Handle, Win32Api.WM_NCLBUTTONDOWN,
                new IntPtr(Win32Api.HTCAPTION), IntPtr.Zero);
        this.DefWndProc(ref msg);
    }
}

文章出处：https://www.cnblogs.com/zhuanghamiao/p/WindowsForm-DragMove.html