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Why do controls delete when copying controls from one panel to the next

I created a template panel to go by when my form loads that holds a record. When adding a new record I have a method that duplicates that template panel and then adds it to my list of panels for each record. Somehow controls are getting deleted from my template panel when I am duplicating it and I have no idea how this is happening. The portion of code doing this is listed below
Panel pn = new Panel()
{
Width = _PNTemp.Width,
Height = _PNTemp.Height,
Left = 0,
Top = 0,
BackColor = _PNTemp.BackColor,
ForeColor = _PNTemp.ForeColor,
AutoScroll = true,
Name = _PNTemp.Name,
Tag = _PrgPanels.Count.ToString()
};
MessageBox.Show(_PNTemp.Controls.Count.ToString());
foreach (Control c in _PNTemp.Controls)
{
pn.Controls.Add(c);
MessageBox.Show(_PNTemp.Controls.Count.ToString());
}
MessageBox.Show(_PNTemp.Controls.Count.ToString());
_PrgPanels.Add(pn);
I put the messagebox.show() in at 3 points to narrow down where it is happening. The first one shows the correct number of controls, the second and third shows a 1/2 the total amount of controls. why is this?

This is because each control can be added to only one parent control. All controls in your template panel are already a child of the template panel. When you try to add these controls to a new panel, the controls will get removed from the template panel.
As per the docs:
A Control can only be assigned to one Control.ControlCollection at a
time. If the Control is already a child of another control it is
removed from that control before it is added to another control.
Which means that you need to create new controls instead of adding those in the template.
An alternative approach is to create a method that returns the template panel. When you need the template panel, just call the method and a new panel will be created:
public static Panel CreateTemplatePanel() {
Panel pn = new Panel();
// set properties, add controls...
return pn;
}

A control can only be on one panel at once. I've added comments inline in your code to help explain whats happening.
Panel pn = new Panel()
{
Width = _PNTemp.Width,
Height = _PNTemp.Height,
Left = 0,
Top = 0,
BackColor = _PNTemp.BackColor,
ForeColor = _PNTemp.ForeColor,
AutoScroll = true,
Name = _PNTemp.Name,
Tag = _PrgPanels.Count.ToString()
};
MessageBox.Show(_PNTemp.Controls.Count.ToString());
//all the controls are still inside _PNTemp
foreach (Control c in _PNTemp.Controls)
{
pn.Controls.Add(c);
MessageBox.Show(_PNTemp.Controls.Count.ToString());
//Each time this runs you remove a control from _PNTemp to pn.
}
//All the controls moved from _PnTemp to pn
MessageBox.Show(_PNTemp.Controls.Count.ToString());
_PrgPanels.Add(pn);

Basic Layout with WindowsForms

How do I create a simple form that has a MenuStrip at the top and a TabControl filling all of the remaining space?
If I go with DockStyle.Top/DockStyke.Fill tabControl fills whole form regardless of MenuStrip:
public MainWindow()
{
initializeComponent();
}
private void initializeComponent()
{
MenuStrip mainMenu = new MenuStrip();
mainMenu.Dock = DockStyle.Top;
TabControl tabs = new TabControl();
tabs.Dock = DockStyle.Fill;
TabPage test = new TabPage("test");
tabs.Controls.Add(test);
Controls.Add(mainMenu);
Controls.Add(tabs);
}

You should change the z-order of mainMenu or tabs. For example you can call:
mainMenu.SendToBack();
//Or
//tabs.BringToFront();
After adding controls to the controls collection.

Another approach through designer, without writing code manually, so your changes will affect design time too
Use Document outline tab and arrange control's hierarchy with your requirements
View -> Other Windows -> Document outline or CTRL+ALT+T

how to make a control visible in a panel?

I want to add a control to my panel in WinForms.
public Form1()
{
InitializeComponent();
PictureBox a = new PictureBox();
a.Left = 100;
a.Top = 150;
a.Width = 50;
a.Height = 50;
a.BackColor = Color.Red;
Controls.Add(a);
}
Without the Panel, this code works perfect. But the Panel blocks the PictureBox, which properties should I change?

Basically, there are few options to achieve that:
1. When you add the controls to your Form like this:
Controls.Add(panel);
Controls.Add(button1);
Controls.Add(button2);
Controls.Add(pictureBox);
They will be shown in this very order: panel on the bottom, buttons between and pictureBox on the top.
2. As it was pointed in the comments, you can use BringToFront() after adding the control.
pictureBox.BringToFront();
This will make the pictureBox to be on top of other things.
3. You can change the order of controls by editing their Z-index, called ChildIndex in WinForms. You can set it with:
Controls.SetChildIndex(pictureBox, __yourIndex__);
4. You can add the pictureBox to your panel with:
panel.Controls.Add(pictureBox);

Why are Anchor properties not being honored within dynamically created nested components?

Let me begin by saying that I have not done a lot of Windows Forms development -- if there is an obvious mistake that I may be making, please don't hesitate to mention it.
Steps to reproduce my issue:
Create a new C# Windows Forms Project using VS 2010 or VS 2012
Using the VS Form Designer, add three FlowLayoutPanel components to the form
Set each FlowLayoutPanel to have the same height as the form and approximately 1/3 the width of the form
Position each FlowLayoutPanel so that they do not overlap each other horizontally and collectively consume approximately the entire area of the Form.
The leftmost FlowLayoutPanel is configured to have an Anchor of Top, Bottom, Left
The middle FlowLayoutPanel is configured to have an Anchor of Top, Bottom
The rightmost FlowLayoutPanel is configured to have an Anchor of Top, Bottom, Right
Add an event for Form_Shown:
private void Form1_Shown(object sender, EventArgs e)
{
Panel p = new Panel();
p.BorderStyle = BorderStyle.FixedSingle;
p.Width = 200;
p.Height = 100;
Label label1 = new Label();
label1.BorderStyle = BorderStyle.FixedSingle;
label1.Text = "Hello";
label1.Anchor = AnchorStyles.Top;
Label label2 = new Label();
label2.BorderStyle = BorderStyle.FixedSingle;
label2.Text = "World!";
label2.Anchor = AnchorStyles.Bottom;
p.Controls.Add(label1);
p.Controls.Add(label2);
middleFlow.Controls.Add(p); // add to the center most FlowLayoutPanel on Form1
}
The result seems to be that label1 is placed on top of label2, despite label2 being added second. Moreover, the anchor values seem to be ignored (as label1 is covering label2 when I intend for them to be anchored to the top and bottom of the Panel component, respectively)
If I use the Dock property instead of the Anchor property, the behavior is as desired. Why does the Anchor property not work in this situation?
Also, is there a way to anchor components to other components? I notice as I increase the size of my Form at runtime, horizontal "gaps" between panels appear. Ideally, I would like the panels to grow together, preventing any gaps/whitespace between them horizontally?
Thanks in advance for any suggestions or tips.

I'm still starting to learn c# and winforms, so the following may not be optimal but it does what you required.
Handled the labels with Dock=Top. Note that the labels are switched so that label1 is on top of label2, i.e., registering label1 last pushes down the already registered label2.
The positioning of the three panels is done without anchors and docks with an event handler for resize. Setting the size of the form after that raises a resize event. Colored to see the components.
using System;
using System.Drawing;
using System.Windows.Forms;
public class ThreePanel : Form {
FlowLayoutPanel leftFlow;
FlowLayoutPanel middleFlow;
FlowLayoutPanel rightFlow;
public ThreePanel(){
leftFlow = new FlowLayoutPanel() {
BackColor = Color.Yellow
};
middleFlow = new FlowLayoutPanel() {
BackColor = Color.LightGreen
};
rightFlow = new FlowLayoutPanel() {
BackColor = Color.LightBlue
};
this.Controls.Add(rightFlow);
this.Controls.Add(middleFlow);
this.Controls.Add(leftFlow);
this.Load += (s,e)=>Form1_Shown(s,e);
this.Resize += (s,e)=>{
int w=this.Width/3;
leftFlow.Width=middleFlow.Width
=rightFlow.Width=w;
leftFlow.Height=middleFlow.Height
=rightFlow.Height=this.Height;
leftFlow.Location=new Point(0,0);
middleFlow.Location=new Point(w,0);
rightFlow.Location=new Point(2*w,0);
};
this.Size = new Size(750,450);
}
private void Form1_Shown(object sender, EventArgs e)
{
Panel p = new Panel() {
BorderStyle = BorderStyle.FixedSingle,
Width = 200,
Height = 100,
BackColor = Color.Fuchsia,
};
Label label1 = new Label() {
BorderStyle = BorderStyle.FixedSingle,
Text = "Hello",
Dock = DockStyle.Top
};
Label label2 = new Label() {
BorderStyle = BorderStyle.FixedSingle,
Text = "World!",
Dock = DockStyle.Top
};
p.Controls.Add(label2);
p.Controls.Add(label1);
// add to the center most FlowLayoutPanel on Form1
middleFlow.Controls.Add(p);
}
public static void Main()
{
Application.Run(new ThreePanel());
}
}

I would expect exactly the behaviour that you mentioned.
The Anchor property only tells the parent container that the label should be sticked
to the parent. In your case AnchorStyles.Top means stick the label to the top and leave it there if the parent moves or resizes.
You did not specify dimensions or positions for the labels, so both overlapp.
The z-order of the controls is created implicitly from the order when added to middleFlow.Controls. You can check this using VS forms designer. Select "Bring to Front" or "Send to Back" and watch how the x.designer.cs changes.
Why it is in reverse order is one of the little .net secrets. The workaround is to change the order. Sometimes it is easier to do it manually than in the designer.

How do I remove a specific panel through event handling in my FlowlayoutPanel for my Windows Form Application?

For my C# Windows Form Application, I have created a flowlayoutpanel that contains several panels. Inside the panel, I have a button "Clear" for each and every single panel.
How do I write the event handler for the code for the button "Clear" such that once I have click the button, the panel would sort of be "Removed" from the flowlayoutpanel.
This is a short part of the code of the adding of panels to the flowlayoutpanel.
nFlowPanel.Controls.Add(createNotificationPanel());
nFlowPanel.Controls.Add(createNotificationPanel());
nFlowPanel.Controls.Add(createNotificationPanel());
nFlowPanel.Controls.Add(createNotificationPanelImpt());
nFlowPanel.Controls.Add(createNotificationPanelImpt());
and this is the code for the button "Clear"
Button btnClear = new Button
{
Text = "Clear",
Name = "btnClear",
Location = new Point(416, 17)
};
p.Controls.Add(btnClear);
btnClear.Click += new EventHandler(buttonClear_Click);
So what should i write in the following method to have the effect of removing e.g. the second panel that was added in the first part of code I have written?
void buttonClear_Click(object sender, EventArgs e)
{
throw new NotImplementedException();
}
EDIT
the code for creating my panel is
var p = new Panel
{
BorderStyle = BorderStyle.FixedSingle ,
Size = new Size(506,100),
Name = "notifyPanel"
};
and the code for creating my FlowLayoutPanel is
var nFlowPanel = new FlowLayoutPanel
{
FlowDirection = FlowDirection.TopDown,
WrapContents = false,
AutoScroll = true,
Size = new Size(530, 377),
Location = new Point(13, 145)
};
and the code for my button clear is
void buttonClear_Click(object sender, EventArgs e)
{
var button = (Control)sender;
var panel = button.Parent.Controls["notifyPanel"];
panel.Dispose();
}
however it gives the error
Object reference not set to an instance of an object.
on the panel.Dispose() line.
anyone can help?

The Controls.Remove() method is very dangerous, it doesn't dispose the control. Which will live on, moved to the so-called parking window, using up both Windows and managed resources. After a bit less than 10,000 times doing this it crashes your program when Windows is no longer willing to let you create any more windows.
Call the control's Dispose() method instead. That also automatically removes the control from its container.
void buttonClear_Click(object sender, EventArgs e)
{
var panel = nFlowPanel.Controls["notifyPanel"];
panel.Dispose();
}

You can do it like this:
nFlowPanel.Controls.Remove((sender as Button).Parent);

I will suggest you to use List for this. Before adding Panels in the FlowLayoutpanel, add them in the List. Then just remove the indexed panel from the flowlayoutpanel.
Panel pnlTemp = (panel)list[index];
nFlowPanel.Controls.Remove(pnlTemp);
To get the index of the button you have to add your buttons also to your list and after clicking any button, search the button in the list and get the index of the button where it is saved in the list. If my code is unclear, let me know. but I feel your task is that complex. I am not sure but this link may be of some help.
Hope it helps.