c# - ObjectDisposedException when moving form -

i made custom form.

now i'm trying implement feature drag form around while holding titlebar. throws exception:

system.objectdisposedexception

has idea problem is?

this code:

    [dllimportattribute("user32.dll")]     public static extern int sendmessage(intptr hwnd, int msg, int wparam, int lparam);     [dllimportattribute("user32.dll")]     public static extern bool releasecapture();      form form;     button buttoncancel;     button buttonok;      dialogresult inputbox(string title, string prompttext, ref string value)     {          form = new form();         buttoncancel = new button();         buttonok = new button();          label label = new label();         textbox textbox = new textbox();          panel titlebar = new panel();         label lbltitle = new label();         panel pnlexit = new panel();         label lblexit = new label();           form.text = title;         label.text = prompttext;         textbox.text = value;          buttonok.text = "ok";         buttoncancel.text = "cancel";         buttonok.dialogresult = dialogresult.ok;         buttoncancel.dialogresult = dialogresult.cancel;          label.setbounds(9, 20, 372, 13);         textbox.setbounds(12, 36, 372, 20);         buttonok.setbounds(228, 72, 75, 23);         buttoncancel.setbounds(309, 72, 75, 23);         buttoncancel.location = new point(250, 100);         buttoncancel.parent = form;         buttoncancel.backcolor = colortranslator.fromhtml("#cddc39");         buttoncancel.flatstyle = flatstyle.flat;         buttoncancel.flatappearance.bordersize = 0;         buttoncancel.mouseclick += buttoncancel_mouseclick;          buttonok.location = new point(170, 100);         buttonok.parent = form;         buttonok.backcolor = colortranslator.fromhtml("#cddc39");         buttonok.flatstyle = flatstyle.flat;         buttonok.flatappearance.bordersize = 0;           form.height = 150;         form.width = 350;         form.backcolor = colortranslator.fromhtml("#455a64");         form.formborderstyle = formborderstyle.none;         form.autosize = false;         form.startposition = formstartposition.centerscreen;         form.acceptbutton = buttonok;         form.cancelbutton = buttoncancel;           titlebar.width = form.width;         titlebar.height = 25;         titlebar.backcolor = colortranslator.fromhtml("#37474f");         titlebar.parent = form;         titlebar.controls.add(pnlexit);         titlebar.mousedown += titlebar_mousedown;          lblexit.text = "x";         lblexit.font = new font("arial", 9.5f, fontstyle.bold);         lblexit.textalign = contentalignment.middlecenter;         lblexit.dock = dockstyle.fill;         lblexit.mouseclick += lblexit_click;          pnlexit.height = titlebar.height - 10;         pnlexit.width = 30;         pnlexit.backcolor = colortranslator.fromhtml("#cddc39");         pnlexit.location = new point(titlebar.width - 33, 0);         pnlexit.parent = titlebar;         pnlexit.controls.add(lblexit);          lbltitle.parent = titlebar;         lbltitle.text = title;         lbltitle.forecolor = colortranslator.fromhtml("#cddc39");         lbltitle.font = new font("arial",  9.5f, fontstyle.bold);         lbltitle.location = new point(5, 3);          label.autosize = true;         label.location = new point(25, 50);         label.parent = form;         label.forecolor = color.white;          textbox.parent = form;         textbox.location = new point(25, 65);         textbox.width = 300;          dialogresult dialogresult = form.showdialog();         value = textbox.text;         console.writeline("value = " + value);         return dialogresult;       }      private void titlebar_mousedown(object sender, mouseeventargs e)     {         if (e.button == mousebuttons.left)         {             releasecapture();             sendmessage(handle, wm_nclbuttondown, ht_caption, 0);         }     }      private  void buttoncancel_mouseclick(object sender, mouseeventargs e)     {        // throw new notimplementedexception();     }      private  void lblexit_click(object sender, mouseeventargs e)     {         form.close();     }