How to move and resize form with no border?

private bool dragging;
private bool resizing;
private bool resizingUp;
private bool resizingDown;
private bool resizingLeft;
private bool resizingRight;
private int border = 4;
private Size previousSize;
private Point previousLocation;
private Point offset;

private void Form1_MouseDown(object sender, MouseEventArgs e)
{
dragging = true;
offset = e.Location;
if (resizing)
{
previousSize = this.Size;
previousLocation = this.Location;
}
}
private void Form1_MouseUp(object sender, MouseEventArgs e)
{
dragging = false;
resizing = false;
resizingUp = false;
resizingDown = false;
resizingLeft = false;
resizingRight = false;
}
private void Form1_MouseMove(object sender, MouseEventArgs e)
{
if (dragging)
{
if (resizing)
{
setLabelInfo();
Point currentScreenPos = PointToScreen(e.Location);
if (resizingLeft)
{
if (resizingUp)
{
this.Width = previousLocation.X + previousSize.Width - currentScreenPos.X + offset.X;
this.Height = previousLocation.Y + previousSize.Height - currentScreenPos.Y + offset.Y;
this.Location = new Point
(previousLocation.X + previousSize.Width - this.Width,
previousLocation.Y + previousSize.Height - this.Height);
}
else if (resizingDown)
{
this.Width = previousLocation.X + previousSize.Width - currentScreenPos.X + offset.X;
this.Height = currentScreenPos.Y - previousLocation.Y + previousSize.Height - offset.Y;
this.Location = new Point
(previousLocation.X + previousSize.Width - this.Width,
previousLocation.Y);
}
else
{
this.Width = previousLocation.X + previousSize.Width - currentScreenPos.X + offset.X;
this.Location = new Point(previousLocation.X + previousSize.Width - this.Width, previousLocation.Y);
}
}
else if (resizingRight)
{
if (resizingUp)
{
this.Width = currentScreenPos.X - previousLocation.X + previousSize.Width - offset.X;
this.Height = previousLocation.Y + previousSize.Height - currentScreenPos.Y + offset.Y;
this.Location = new Point
(previousLocation.X,
previousLocation.Y + previousSize.Height - this.Height);
}
else if (resizingDown)
{
this.Width = currentScreenPos.X - previousLocation.X + previousSize.Width - offset.X;
this.Height = currentScreenPos.Y - previousLocation.Y + previousSize.Height - offset.Y;
}
else
{
this.Width = currentScreenPos.X - previousLocation.X + previousSize.Width - offset.X;
}
}
else if (resizingUp)
{
this.Height = previousLocation.Y + previousSize.Height - currentScreenPos.Y + offset.Y;
this.Location = new Point(previousLocation.X, previousLocation.Y + previousSize.Height - this.Height);
}
else if (resizingDown)
{
this.Height = currentScreenPos.Y - previousLocation.Y + previousSize.Height - offset.Y;
}
}
else
{
Point currentScreenPos = PointToScreen(e.Location);
Location = new Point
(currentScreenPos.X - offset.X,
currentScreenPos.Y - offset.Y);
}
}
else
{
if (e.X <= border)
{
resizing = true;
resizingUp = false;
resizingDown = false;
resizingLeft = true;
resizingRight = false;

if (e.Y <= border)
{
this.Cursor = Cursors.SizeNWSE;
resizingUp = true;
}
else if (e.Y >= this.Height - border)
{
this.Cursor = Cursors.SizeNESW;
resizingDown = true;
}
else
{
this.Cursor = Cursors.SizeWE;
}
}
else if (e.X >= this.Width - border)
{
resizing = true;
resizingUp = false;
resizingDown = false;
resizingLeft = false;
resizingRight = true;

if (e.Y <= border)
{
this.Cursor = Cursors.SizeNESW;
resizingUp = true;
}
else if (e.Y >= this.Height - border)
{
this.Cursor = Cursors.SizeNWSE;
resizingDown = true;
}
else
{
this.Cursor = Cursors.SizeWE;
}
}
else if (e.Y <= border)
{
resizing = true;
resizingUp = true;
resizingLeft = false;
resizingRight = false;
this.Cursor = Cursors.SizeNS;
}
else if (e.Y >= this.Height - border)
{
resizing = true;
resizingDown = true;
resizingLeft = false;
resizingRight = false;
this.Cursor = Cursors.SizeNS;
}
else
{
this.Cursor = Cursors.Default;
resizing = false;
resizingUp = false;
resizingDown = false;
resizingLeft = false;
resizingRight = false;
}
}
}