C ++ clr - error creating user control in visual studio

I am having an error when creating a user control using c ++ clr, I compile the solution and the user control appears but when I am going to add it it gives the following error: "Failed to load item from the toolbox" .

I practically leave this code in myusercontrol.cpp

#include "MyUserControl.h"

using namespace System;
using namespace System::ComponentModel;
using namespace System::Collections;
using namespace System::Windows::Forms;
using namespace System::Data;
using namespace System::Drawing;

[STAThreadAttribute]
int userctrl(array<System::String ^> ^args)
{
    Application::EnableVisualStyles();
    Application::SetCompatibleTextRenderingDefault(false);
    Xploit::MyUserControl mainform;

    return 0;
}

Someone has an idea