We can not delete hidden fields directly from sharepoint list forms. In order to delete it, we need to set CanToggleHidden attribute to true & then we can unhide the field & can delete it using Object Model.
Add System.Reflection namespace.
using (SPSite site = new SPSite(site url))
{
using (SPWeb web = site.OpenWeb())
{
SPList testList = web.Lists["Test"];
web.AllowUnsafeUpdates = true;
SPField objTitle = testList.Fields["Title"];
Type type = objTitle.GetType();
MethodInfo mi = type.GetMethod("SetFieldBoolValue",BindingFlags.NonPublic | BindingFlags.Instance);
mi.Invoke(objTitle, new object[] { "CanToggleHidden", true });
objTitle.Hidden = true; //objTitle.Hidden = false;
objTitle.Update();
}
}
Once CanToggleHidden attribute is set to "true" , so you can unhide the field as you wish. and further you can delete the hidden field.
