'Why does Visual C++ Designer not work after I added a control to my form?

My wanted to turn on double buffering in a panel, but the only way we could get the DoubleBuffered property to turn on was to create a new class that inherited from System::Windows::Form::Panel, like so:

#include "stdafx.h"

public ref class CPPIConfig: public System::Windows::Forms::Panel
{
public: CPPIConfig()
        {
            this->DoubleBuffered = true;
        }
};

And our form looks like this, now:

#pragma once
#using <system.drawing.dll>
#include "CPPIConfig.h"

[...]

public ref class C3_User_Interface : public System::Windows::Forms::Form
    {
      [...]
      public: CPPIConfig^ pPPI;
      [...]
    }

void InitializeComponent(void)
    {
        [...]
        this->pPPI = (gcnew CPPIConfig());
        [...]
    }
[...]

It builds and runs, no problem. However, when I try to view the form in design mode now, I'm getting the following error:

C++ CodeDOM parser error: Line: 144, Column: 15 --- Unknown type 'CPPIConfig'. Please make sure that the assembly that contains this type is referenced. If this type is a part of your development project, make sure that the project has been successfully built.

My questions:

Why does design mode not work, even if the code builds and runs? I've tried several clean builds, but that doesn't look to be the issue.
Is there a way I can set DoubleBuffered to true without using this method?

Solution 1:^[1]

Try moving the control initializing below the suspendlayout. This allows the designer to render correctly without the CodeDOM parse error.

Original was something like

#pragma region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
void InitializeComponent(void)
{
    this->lblMessage = (gcnew System::Windows::Forms::Label());
    this->SuspendLayout();
    // lblMessage
    this->lblMessage->Location = System::Drawing::Point(12, 230);
    //.....
}

New format

#pragma region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
void InitializeComponent(void)
{
    this->SuspendLayout();
    // lblMessage
    this->lblMessage = (gcnew System::Windows::Forms::Label());
    this->lblMessage->Location = System::Drawing::Point(12, 230);
    //.....
}

Solution 2:^[2]

If you Google for your error message, you'll find lots of hits:

C++ CodeDOM parser error:  Unknown type 'CPPIConfig'

Please post back if any of these help!

Solution 3:^[3]

I had an inherited class from Panel as well. In my case, I had placed this toolbox item in its own C# project with its own namespace. For reasons unknown, the designer worked at first implementation then broke after I attempted to use the inherited class in a second file.

To fix it, I changed the namespace of the C# project to match the consuming projects namespace, as well as explicitly specified it in the designer code:

Project1::InheritedPanel^

instead of simply

InheritedPanel^

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	SavageFly
Solution 2	Community
Solution 3	Nabeel

'Why does Visual C++ Designer not work after I added a control to my form?

Solution 1:[1]

Solution 2:[2]

Solution 3:[3]

Sources

Related Questions

Solution 1:^[1]

Solution 2:^[2]

Solution 3:^[3]