Ошибки C2227 и C2064. Не знаю как исправить

 L=Convert::ToDouble(L->Text);  //ввод длины волны
R=Convert::ToDouble(R->Text);   //ввод радиуса кривизны
N=Convert::ToDouble(N->Text);   //ввод номера кольца
 
X = R*L*(N-0,5);     //рассчет промежуточного вычисления
radius = sqrt(X);
radius -> Text = System::Convert::ToString(radius);

this->N->BackColor = System::Drawing::SystemColors::MenuBar;
this->N->Location = System::Drawing::Point(417, 230);
this->N->Name = L"N";
this->N->Size = System::Drawing::Size(100, 31);
this->N->TabIndex = 6;
 
// 
// R
// 
this->R->BackColor = System::Drawing::SystemColors::MenuBar;
this->R->Location = System::Drawing::Point(417, 178);
this->R->Name = L"R";
this->R->Size = System::Drawing::Size(100, 31);
this->R->TabIndex = 8;

double R, N, L;
double sqrt(double X);
double X = R*L*(N-0,5); 
double radius = sqrt(X);

private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) 
{
  double _L,        //Длина волны
  _R,     // Радиус кривизны
  _X,     // Результат промежуточного вычисления
  _radius,   // Радиус кольца Ньютона
  _sqrt,
  _N;        //Номер кольца
  _L=Convert::ToDouble(L->Text);    //ввод длины волны
  _R=Convert::ToDouble(R->Text);    //ввод радиуса кривизны
  _N=Convert::ToDouble(N->Text);    //ввод номера кольца
  _X = _R*_L*(_N-0,5);        //рассчет промежуточного вычисления
  _radius = System::Math::Sqrt(_X);
  radius->Text = System::Convert::ToString(_radius);
}

// 
// button1
// 
this->button1->BackColor = System::Drawing::SystemColors::MenuHighlight;
this->button1->Font = (gcnew System::Drawing::Font(L"Verdana", 14.25F, System::Drawing::FontStyle::Bold, System::Drawing::GraphicsUnit::Point, 
    static_cast<System::Byte>(204)));
this->button1->Location = System::Drawing::Point(96, 412);
this->button1->Name = L"button1";
this->button1->Size = System::Drawing::Size(139, 37);
this->button1->TabIndex = 0;
this->button1->Text = L"старт";
this->button1->UseVisualStyleBackColor = true;
this->button1->Click += gcnew System::EventHandler(this, &Form1::button1_Click);
            
// 
// button2
// 
this->button2->BackColor = System::Drawing::SystemColors::MenuHighlight;
this->button2->Font = (gcnew System::Drawing::Font(L"Verdana", 14.25F, System::Drawing::FontStyle::Bold, System::Drawing::GraphicsUnit::Point, 
    static_cast<System::Byte>(204)));
this->button2->Location = System::Drawing::Point(343, 413);
this->button2->Name = L"button2";
this->button2->Size = System::Drawing::Size(142, 36);
this->button2->TabIndex = 1;
this->button2->Text = L"выход";
this->button2->UseVisualStyleBackColor = true;
this->button2->Click += gcnew System::EventHandler(this, &Form1::button2_Click);

this->button1->Click += gcnew System::EventHandler(this, &Form1::button1_Click);
...
this->button2->Click += gcnew System::EventHandler(this, &Form1::button2_Click);