Task no longer runs my code

I am new to the concept of multithreading and I wanted to implement it into my existing code to make some nested foreach loops run faster. After putting it in a task and running it, the code no longer does anything.

var task = Task.Factory.StartNew
            (() =>
                {
                    foreach (Control groupbox in tabControl.SelectedTab.Controls)
                    {
                        if (groupbox is GroupBox)
                        {
                            foreach (Control ctrl in groupbox.Controls)
                            {
                                if (ctrl is Panel)
                                {
                                    foreach (Control c in ctrl.Controls)
                                    {
                                        if (c is CheckBox)
                                            (c as CheckBox).Checked = false;
                                    }
                                }
                                if ((string)ctrl.Tag == "num")
                                    (ctrl as TextBox).Text = Convert.ToString(0);
                                else if (ctrl is TextBox)
                                    (ctrl as TextBox).Text = "";

                                if (ctrl is MaskedTextBox)
                                    (ctrl as MaskedTextBox).Text = "";
                                if (ctrl is ComboBox)
                                    (ctrl as ComboBox).SelectedIndex = 0;
                                if (ctrl is CheckBox)
                                    (ctrl as CheckBox).Checked = false;
                            }
                        }
                    }
                });

Without the var task = Task.Factory.StartNew (() =>...}); the code runs but is obviously not in a task. If anyone can spot what I am doing incorrectly, it would be greatly appreciated. Thanks.