Getting MdiParent Instance From MdiChild - Windows Forms Application

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C++

C++/CLI

VisualC++

Hi, Iam using VC++ 2010. While I want to get the MdiParent-Forms Instance, its giving the error, Really I can't identify my mistake...

My Codes from MdiParent
=======================

#include "For_Student_Detials

private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
For_Student_Detials^ MyStudentDet= For_Student_Detials::GetForm(true,this);
MyStudentDet->MdiParent=this;
MyStudentDet->FormBorderStyle=System::Windows::Forms::FormBorderStyle::None;
MyStudentDet->Dock=DockStyle::Fill;
MyStudentDet->Show();
}

My Codes From MdiChild // CFIS_Main is my Mdi-Container
=========================================================
#any Include Reqd?????

public: static For_Student_Details^ For_Student_Details::_instance = nullptr;
public: static For_Student_Details^ For_Student_Details::GetForm(bool^ IsMDIChild, CFIS_Main^ MyInstFrm) {
if (_instance == nullptr)
    _instance = gcnew For_Student_Details();

if (_instance->IsDisposed)
    _instance = gcnew For_Student_Details();
		
if (IsMDIChild)
    _instance->MdiParent = MyInstFrm;
		
return _instance;
}

From the above code I can't identify my mistake, Does anybody can point me?
Thanks For Helps