A simple example of a border free form movement in C

Start by building an Windows application
Set the FormBorderStyle property of Form1 to Noe

Point mouseOff;// Mouse moves the position variable 
        bool leftFlag;// Whether the flag is left key 
        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                mouseOff = new Point(-e.X, -e.Y); // You get the value of the variable 
                leftFlag = true;                  // Click the left button to mark as true;
            }
        }
        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            if (leftFlag)
            {
                Point mouseSet = Control.MousePosition;
                mouseSet.Offset(mouseOff.X, mouseOff.Y);  // Set the position after the move 
                Location = mouseSet;
            }
        }
        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            if (leftFlag)
            {
                leftFlag = false;// Marked as after mouse release false;
            }
        }