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Show a Winform 'Form' as if it were a usercontrol, within another form

Edit
The answer to This Question, though an obvious solution, is insufficient for this case. I've bolded the reason in my original question explaining why I wanted it 'literally answered' - thanks LarsTech!
My Original Question:
I have a library with 100 WinForms Form screens in it that is 'Beyond My Control' and there are a few I can share in my app. However, my app uses a tab control and I need the content of the forms to appear within the tabs instead of as popups.
When I try to new up one of the forms and add it to the controls collection of a tab, I get this error message:
Top-level control cannot be added to a control.
Anybody know how to get around this? I know there are other ways involving better architecture, but deadlines, backlogs, and rich new customers await. [sigh/]
private void button1_Click(object sender, EventArgs e)
{
//panel1.Controls.Add(new Button());
Form f = new Form();
f.Controls.Add(new CheckBox());
//f.ShowDialog();
panel1.Controls.Add(f);
}

Try turning the TopLevel off:
f.TopLevel = false;
f.FormBorderStyle = FormBorderStyle.None;
f.Visiible = true;
Now it is essentially a UserControl. A word of caution though, since it's a form, it will show up in the Application.OpenForms collection, which is probably not your intention.

You need to set the form's TopLevel property to false, like this:
f.TopLevel = false;
You may also want to set the FormBorderStyle property to None.
f.FormBorderStyle = FormBorderStyle.None;
As mentioned in the comments above, it really would be best, when possible, to make it a UserControl.

how to add vertical scroll bars in tabcontrol/tabpages

I am designing an application in which i am using tab-control, and in one of the tab-page the information i want to display in bigger than the form size, the information is displayed in various text-boxes. i tried by adding following lines in designer code but it is still not working.
this.AutoScroll = true;
this.AutoScrollMargin = new System.Drawing.Size(20, 20);
this.AutoScrollMinSize = new System.Drawing.Size(this.Width, this.Height);
any help would be appreciated.

You have to set the AutoScroll on the TabPage, not the Form, you can do this at design time by selecting your tabpage first, then set the AutoScroll to true in the Properties window, or you can do by code like this:
tabPage1.AutoScroll = true;
//do the same for other tabPages

Notice that "this" refer to whole class (your form).
Increase the value like this:
tab.AutoScrollMinSize = new System.Drawing.Size(1000,1000);
Or you can add panel1 to your tab, then dock it into the tab:
panel1.dock = dockingSyle.Fill;
Now you can make panel1 scrollable.

Visual Studio wont let me remove the maximise/minimise button/icon etc

I have Form1.cs which I have set in properties to be borderless, without an icon, max/min buttons (and the changes are shown visually in Form1.cs), but when I debug/run, all of those controls stay the same as they previously were. The properties are then found in my code under private void InitializeComponent() as this.ShowIcon = false; etc.. Form1.Designer.cs is always empty though, have I messed up some settings somehow that overrides my form1.cs selections?

Have you tried setting the forms .MaximizeBox and .MinimizeBox to false ?
If so, can you please post the contents of that InitializeComponent method.

Winforms have properties like MinimizeBox, MaximizeBox and ShowIcon on the designer if you set then to False. Then you wont require any line of code in private void InitializeComponent()

Design view only show what is set in Form1.Design.cs, and not your custom code (except for some events and properties like resize...) Did you overwrite any design values in your code after you run InitializeComponents?
The easiest way is to cross-reference Form1.

If you're trying to remove the entire title bar you'll want to set the FormBorderStyle to None. If that doesn't work try and set a breakpoint after your form has loaded and check the values to make sure they are what you think they should be. This should not require any coding.

Form.Location doesn't work

I asked this question previously and thought I had it figured out but it still doesn't work.
Form.Show() moves form position slightly
So I have a parent form that opens a bunch of children with show() and then when one is needed I use bringToFront() to display it. The problem is when show() is called the child form is aligned perfectly but when I use bringToFront it moves left and down 1 px which screws with my borders. I have set all the child forms startPosition properties to Manual before show()-ing them. I have set frm.location = new Point(x,y) when bringing to front. I've also tried explicity setting frm.location when show()-ing also. It still moves it left and down 1 px when I bringToFront(). Is there something with bringToFront() that doesn't let me change the location property of the form? Here is my code:
if (myNewForm != null)
{
myNewForm.MdiParent = this;
bool isFormOpen = false;
foreach (Form frm in Application.OpenForms)
{
if (frm.GetType() == myNewForm.GetType())
{
frm.WindowState = FormWindowState.Maximized;
frm.BringToFront();
frm.Location = new Point(-4, -30);
isFormOpen = true;
break;
}
}
if (!isFormOpen)
{
myNewForm.StartPosition = FormStartPosition.Manual;
myNewForm.Show();
}
}
EDIT: Ok so apparently Microsoft has a bug that lets StartPosition only work for ShowDialog() and not Show() but refuses to fix it: http://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=107589
But my application needs to keep all the different forms open and just bring them to the front when needed...so ShowDialog() could not be appropriately used in this instance correct? So what options do I have? Any?

If you wish to set the form location, you have to set the form's WindowState to Normal (on any other setting, the location is set for you according to the rules of that setting, so your value is ignored), and its StartPosition to Manual.
frm.WindowState = FormWindowState.Normal;
frm.StartPosition = FormStartPosition.Manual;
frm.BringToFront();
frm.Location = new Point(-4, -30);

I suppose the forms are moved by the code that handles the Show() (and BringToFront) requests, so you really cannot set the form's location - neither before nor after calling the method - because the form location will be updated after the code in your main window has executed (and left control back to the window message pump, in Win32 terms, basically).
I would use a subclass of Form for each of your forms and then add an explicit Point property that indicates the fixed position where that particular form is expected to be. Inside this class, override the OnShown virtual method (or perhaps the OnActivated method too) and simply update this.Location with the correct location.
That should force the forms to the correct position, even if some code inside windows forms changes it at some time.

Have you tried:
this.Location
or
Form.ActiveForm.Location ?

What about using a p/Invoke to MoveWindow? The link provided includes a C# example.

Have you tried showing the form, and then adjusting the Location?
Edit: Or, have you tried adjusting the Left and Top properties?

Set a disabled TextBox's ForeColor to be the same as its BackColor in C#

How do I set a disabled TextBox's current text color to be the same as its current background color in C#?
Simply doing txtLala.ForeColor = txtLala.BackColor does not seems to work.

This works:
txtLala.Text = "Red";
txtLala.BackColor = System.Drawing.Color.Red;
txtLala.ForeColor = txtLala.BackColor;
txtLala.ReadOnly = true;
Try setting the color, before the readonly. And also check how you are setting the color!
EDIT
Try this
txtLala.Attributes.Add("style","background-color:Red;color:Red");
If you are trying to make it invisible, you know you can set it as
txtLala.Visible = False;
EDIT II
I finally tried
txtLala.Enabled = false;
... you see that grey shadow color! I don't think you can mess with that, it looks to be a browser property setting.
Why not set as ReadOnly or Visible = False?
Maybe you have a good reason for Enabled = false
But you should note:
Use the Enabled property to specify or determine whether a control is functional. When set to false, the control appears dimmed, preventing any input from being entered in the control.
Note The ability to enable or disable functionality is always available. However, dimming and locking the control only works in Microsoft Internet Explorer version 4 and later.
This property propagates down the control hierarchy. Therefore, disabling a container control will disable all child controls within that container.
Note Not all controls support this property. See the indivual controls for details.

It seems to only work for TextBox that is read only. If it is disabled (.Enabled = false). It does not seems to work.

If this is a readonly textbox, you need to explicitly set your BackColor first, then your statement will work.
txtLala.BackColor = System.Drawing.SystemColors.Info;
txtLala.ForeColor = txtLala.BackColor;
Ref: http://bytes.com/groups/net-c/233961-read-only-textbox
Then again, if it's readonly, a label might be better. If you're trying to hide it, perhaps setting .Visible = false would be better still.
Edit: This seems to be a common question on the web. With respect to winforms: This site suggests dropping the box into a frame and setting Enabled = false on the frame, not the textbox. Once you do that, you may be able to maintain control of the forecolor.