Ошибка "non-standard syntax; use ‘&’ to create a pointer to member"

#pragma once
 
#include <stdio.h>
#include <cmath>
#include <string.h>
#include <stdlib.h>
 
 
namespace calcilator {
 
    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
    {
    public:
        MyForm(void)
        {
            InitializeComponent();
            //
            //TODO: Add the constructor code here
            //
        }
 
    protected:
        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        ~MyForm()
        {
            if (components)
            {
                delete components;
            }
        }
    private: System::Windows::Forms::TextBox^ textBox1;
 
    private: System::Windows::Forms::TextBox^ textBox2;
    private: System::Windows::Forms::TextBox^ textBox3;
    private: System::Windows::Forms::Button^ button1;
    private: System::Windows::Forms::ContextMenuStrip^ contextMenuStrip1;
    private: System::ComponentModel::IContainer^ components;
 
 
    protected:
 
    private:
        /// <summary>
        /// Required designer variable.
        /// </summary>
 
 
#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->components = (gcnew System::ComponentModel::Container());
            this->textBox1 = (gcnew System::Windows::Forms::TextBox());
            this->textBox2 = (gcnew System::Windows::Forms::TextBox());
            this->textBox3 = (gcnew System::Windows::Forms::TextBox());
            this->button1 = (gcnew System::Windows::Forms::Button());
            this->contextMenuStrip1 = (gcnew System::Windows::Forms::ContextMenuStrip(this->components));
            this->SuspendLayout();
            // 
            // textBox1
            // 
            this->textBox1->Location = System::Drawing::Point(54, 56);
            this->textBox1->Name = L"textBox1";
            this->textBox1->Size = System::Drawing::Size(100, 20);
            this->textBox1->TabIndex = 0;
            this->textBox1->TextChanged += gcnew System::EventHandler(this, &MyForm::textBox1_TextChanged);
            // 
            // textBox2
            // 
            this->textBox2->Location = System::Drawing::Point(54, 92);
            this->textBox2->Name = L"textBox2";
            this->textBox2->Size = System::Drawing::Size(100, 20);
            this->textBox2->TabIndex = 2;
            this->textBox2->TextChanged += gcnew System::EventHandler(this, &MyForm::textBox2_TextChanged);
            // 
            // textBox3
            // 
            this->textBox3->Location = System::Drawing::Point(54, 129);
            this->textBox3->Name = L"textBox3";
            this->textBox3->Size = System::Drawing::Size(100, 20);
            this->textBox3->TabIndex = 3;
            this->textBox3->TextChanged += gcnew System::EventHandler(this, &MyForm::textBox3_TextChanged);
            // 
            // button1
            // 
            this->button1->Location = System::Drawing::Point(79, 181);
            this->button1->Name = L"button1";
            this->button1->Size = System::Drawing::Size(75, 23);
            this->button1->TabIndex = 4;
            this->button1->Text = L"button1";
            this->button1->UseVisualStyleBackColor = true;
            this->button1->Click += gcnew System::EventHandler(this, &MyForm::button1_Click);
            // 
            // contextMenuStrip1
            // 
            this->contextMenuStrip1->Name = L"contextMenuStrip1";
            this->contextMenuStrip1->Size = System::Drawing::Size(61, 4);
            // 
            // MyForm
            // 
            this->AutoScaleDimensions = System::Drawing::SizeF(6, 13);
            this->AutoScaleMode = System::Windows::Forms::AutoScaleMode::Font;
            this->ClientSize = System::Drawing::Size(412, 336);
            this->Controls->Add(this->button1);
            this->Controls->Add(this->textBox3);
            this->Controls->Add(this->textBox2);
            this->Controls->Add(this->textBox1);
            this->Name = L"MyForm";
            this->Text = L"MyForm";
            this->ResumeLayout(false);
            this->PerformLayout();
 
        }
#pragma endregion
    private: System::Void textBox1_TextChanged(System::Object^ sender, System::EventArgs^ e) {  
    } // a
    private: System::Void textBox2_TextChanged(System::Object^ sender, System::EventArgs^ e) {
    } // b  
    private: System::Void textBox3_TextChanged(System::Object^ sender, System::EventArgs^ e) {
    } // c
    
    private: System::Void button1_Click(System::Object^ sender, System::EventArgs^ e) {
        double a = Convert::ToInt32(textBox1_TextChanged );
        double b = Convert::ToInt32(textBox2_TextChanged );
        double c = Convert::ToInt32(textBox3_TextChanged );
 
        if ((b * b - 4 * a * c) >= 0)
        {
            double x = (-1 * b + sqrt(b * b - 4 * a * c)) / (2 * a);
            double x1 = (-1 * b - sqrt(b * b - 4 * a * c)) / (2 * a);
            MessageBox::Show("Первый корень равен" + x + "Второй корень равне" + x1);
        }
        else
        {
            MessageBox::Show("Корней нет");
        }
}
};
}