C ++ gcnew错误

Question

我有这个程序叫做图片搜索者（我知道它是愚蠢的）。它是我的第一个C ++表单应用程序。我在visualbasic c ++ 2010中制作它。我有3种形式我有表单1连接到表单2但是当我尝试将表单2连接到表单3时它给出了我的错误：

1>c:\users\naqeeb\documents\visual studio\search for pictures\search for                                  
pictures\Form2.h(143): error C2065: 'Form3' : undeclared identifier
1>c:\users\naqeeb\documents\visual studio\search for pictures\search for     
pictures\Form2.h(143): error C2065: 'f3' : undeclared identifier
1>c:\users\naqeeb\documents\visual studio\search for pictures\search for     
pictures\Form2.h(143): error C2061: syntax error : identifier 'Form3'
1>c:\users\naqeeb\documents\visual studio\search for pictures\search for 
pictures\Form2.h(144): error C2065: 'f3' : undeclared identifier
1>c:\users\naqeeb\documents\visual studio\search for pictures\search for 
pictures\Form2.h(144): error C2227: left of '->Show' must point to   
class/struct/union/generic type
1>          type is ''unknown-type''
1>  Generating Code...
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

表示Form2的代码：

#pragma once



#include "stdAfx.h"
#include "Form3.h"



namespace Searchforpictures {

using namespace std;
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 Form2
/// </summary>
public ref class Form2 : public System::Windows::Forms::Form
{
public:
    Form2(void)
    {
        InitializeComponent();
        //
        //TODO: Add the constructor code here
        //
    }

protected:
    /// <summary>
    /// Clean up any resources being used.
    /// </summary>
    ~Form2()
    {
        if (components)
        {
            delete components;
        }
    }
private: System::Windows::Forms::TextBox^  input;
protected: 

protected: 
private: System::Windows::Forms::Button^  search;
private: System::Windows::Forms::Label^  label1;
private: System::Windows::Forms::Label^  label2;


private:
    /// <summary>
    /// Required designer variable.
    /// </summary>
    System::ComponentModel::Container ^components;

#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->input = (gcnew System::Windows::Forms::TextBox());
        this->search = (gcnew System::Windows::Forms::Button());
        this->label1 = (gcnew System::Windows::Forms::Label());
        this->label2 = (gcnew System::Windows::Forms::Label());
        this->SuspendLayout();
        // 
        // input
        // 
        this->input->Location = System::Drawing::Point(21, 56);
        this->input->Name = L"input";
        this->input->Size = System::Drawing::Size(371, 20);
        this->input->TabIndex = 0;
        this->input->TextChanged += gcnew System::EventHandler(this,  
&Form2::textBox1_TextChanged);
        // 
        // search
        // 
        this->search->Enabled = false;
        this->search->Location = System::Drawing::Point(432, 56);
        this->search->Name = L"search";
        this->search->Size = System::Drawing::Size(79, 21);
        this->search->TabIndex = 1;
        this->search->Text = L"Search";
        this->search->UseVisualStyleBackColor = true;
        this->search->Click += gcnew System::EventHandler(this,   
                     &Form2::search_Click);
        // 
        // label1
        // 
        this->label1->AutoSize = true;
        this->label1->Location = System::Drawing::Point(31, 40);
        this->label1->Name = L"label1";
        this->label1->Size = System::Drawing::Size(100, 13);
        this->label1->TabIndex = 2;
        this->label1->Text = L"Search for a picture";
        // 
        // label2
        // 
        this->label2->AutoSize = true;
        this->label2->Location = System::Drawing::Point(3, 5);
        this->label2->Name = L"label2";
        this->label2->Size = System::Drawing::Size(93, 13);
        this->label2->TabIndex = 3;
        this->label2->Text = L"Welcome Naqeeb";
        // 
        // Form2
        // 
        this->AutoScaleDimensions = System::Drawing::SizeF(6, 13);
        this->AutoScaleMode = System::Windows::Forms::AutoScaleMode::Font;
        this->ClientSize = System::Drawing::Size(523, 109);
        this->Controls->Add(this->label2);
        this->Controls->Add(this->label1);
        this->Controls->Add(this->search);
        this->Controls->Add(this->input);
        this->MaximizeBox = false;
        this->MinimizeBox = false;
        this->Name = L"Form2";
        this->Text = L"Search for Pictures";
        this->ResumeLayout(false);
        this->PerformLayout();

    }
#pragma endregion
private: System::Void textBox1_TextChanged(System::Object^  sender,     
System::EventArgs^  e) {
        search->Enabled=true;    

         }
private: System::Void search_Click(System::Object^  sender, System::EventArgs^  e)  
{
 if (input->Text=="something") {
                 MessageBox::Show("...");
             }
             else if (input->Text=="sky") {

                 MessageBox::Show("...");

             } else {

            this->Hide();
            Form3^ f3 = gcnew Form3();
            f3->Show();

             //}             

             }

};
}`