How to add usercontrol to a panel on mainform from another form

See more:

C#

user-controls

form

.NET4.6

Hello guys !

I have 2 form and 3 UserControl(Campain_Overview , Campain_Post, Campain_Interact).

1 - MainForm contain panel2 hold UserControl name Campain_Overview, In this UserControl contain button call "Add Campain".

2 - When I click on "Add Campain" Button, It's show another form diaglog call "Add Campain".This form contain 2 button : "Campain Post" and "Campain Interact".

3 - So I want If I click on button "Campain Post", It's close "Add Campain" form, then load userControl Campain_Post into panel2 in Mainform.

4 - Similar to button "Campain Interact", Close "Add Campain" form, then load userControl Campain_Interact into panel2 in Mainform.

This is pic form my work :
http://prntscr.com/mfpt8p[^]


Can you guys help me ? And show me in detail with code, because I'm a baby in programing, and English is not my main language !

Thanks you

What I have tried:

This is in AddCampain.cs form. Even click generate by designer. But When I run this, it's said "Object Reference not set to an instance of an object" at this line :

pnl.panel2.Controls.Add(camPost);

pnl.panel2.Controls.Add(camInteract);

private void CampainPost_Click(object sender, EventArgs e) {


           MainForm pnl = (MainForm)ParentForm;

           Campain_Post camPost = new Campain_Post();
           pnl.panel2.Controls.Add(camPost);
           camPost.Dock = DockStyle.Fill;
           camPost.BringToFront();
           Close();

       }

<pre> private void CampainInteraction_Click(object sender, EventArgs e) {


            MainForm pnl = (MainForm)ParentForm;
            Campain_Interaction camInteract = new Campain_Interaction ();
            pnl.panel2.Controls.Add(camInteract);
            camInteract .Dock = DockStyle.Fill;
            camInteract .BringToFront();
            Close();

        }