c# - Remove controlBox, minimizeBox, and maximizeBox in full screen -

i trying create interface has mdi child forms open in full screen mode within parent , controlbox, minimizebox, , maximizebox show in full screen though have them set false. know how fix this?

here code using switch between screens (children forms) should open in full screen mode because default set them with, need rid of minimize, maximize, , control buttons.

public partial class parent : form {     form activeform = new form2();     public parent()     {         initializecomponent();     }      private void parent_load(object sender, eventargs e)     {         activeform.mdiparent = this;         activeform.show();     }      private void toolstripbutton1_click(object sender, eventargs e)     {         if(toolstriptextbox1.text == "1")         {             activeform.close();             activeform = new form2();             activeform.mdiparent = this;             activeform.show();         }         if (toolstriptextbox1.text == "2")         {             activeform.close();             activeform = new form3();             activeform.mdiparent = this;             activeform.show();         }     } }