Наследование: System.Windows.Forms.Form
        private void btnAlign_Click(object sender, EventArgs e)
        {
            var alignForm = new AlignForm {
                Location = MousePosition
            };

            alignForm.AlignFormClick += AlignFormClick;
            alignForm.Show(this);
        }
 private void btnAlign_Click(object sender, EventArgs e)
 {
     var alignForm = new AlignForm {Location = MousePosition};
     alignForm.AlignFormClick += AlignFormClick;
     alignForm.Show(this);
 }