Namespace with 2 forms

I have namespace "Client" with form MainWindow and form MyForm

MainWindow creates MyForm.

in MyForm.h i write this:

#pragma once

namespace Client {

    using namespace System;
    using namespace System::ComponentModel;
    using namespace System::Collections;
    using namespace System::Windows::Forms;
    using namespace System::Data;
    using namespace System::Drawing;
    /// <summary>
    /// Summary for MyForm
    /// </summary>
    public ref class MyForm : public System::Windows::Forms::Form
    {
    private:
        MainWindow ^f;  //this is my problem
    public:
        MyForm(void)
        {
            InitializeComponent();
        }
......
......
......
}

After compile, i have this error in line MainWindow ^f;:

1>c:\users\user\desktop\testlist\client\MyForm.h(17): error C2143: syntax error : missing ';' before '^'
1>c:\users\user\desktop\testlist\client\MyForm.h(17): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>  MyForm.cpp

If i write this Client::MainWindow ^f;:

1>c:\users\user\desktop\testlist\client\MyForm.h(17): error C2039: 'MainWindow' : is not a member of 'Client'
1>c:\users\user\desktop\testlist\client\MyForm.h(17): error C2143: syntax error : missing ';' before '^'
1>c:\users\user\desktop\testlist\client\MyForm.h(17): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>  MainWindow.cpp

1 errror - The form is a member of Client, why?

How can i fix this problem?