Error LNK2031: unable to generate p/invoke for "extern "C" enum CURLcode __clrcall curl_easy_setopt

1>------ Build started: Project: 333, Configuration: Debug Win32 ------
1>Build started 13.11.2015 23:39:58.
1>InitializeBuildStatus:
1>  Touching "Debug\333.unsuccessfulbuild".
1>GenerateTargetFrameworkMonikerAttribute:
1>Skipping target "GenerateTargetFrameworkMonikerAttribute" because all output files are up-to-date with respect to the input files.
1>ClCompile:
1>  All outputs are up-to-date.
1>  All outputs are up-to-date.
1>  All outputs are up-to-date.
1>CoreResGen:
1>  No resources are out of date with respect to their source files. Skipping resource generation.
1>ResourceCompile:
1>  All outputs are up-to-date.
1>333.obj : error LNK2031: unable to generate p/invoke for "extern "C" enum CURLcode __clrcall curl_easy_setopt(void *,enum CURLoption,...)" (?curl_easy_setopt@@$$J0YM?AW4CURLcode@@PAXW4CURLoption@@ZZ); calling convention missing in metadata
1>333.obj : error LNK2020: unresolved token (0A000011) "extern "C" enum CURLcode __clrcall curl_easy_setopt(void *,enum CURLoption,...)" (?curl_easy_setopt@@$$J0YM?AW4CURLcode@@PAXW4CURLoption@@ZZ)
1>333.obj : error LNK2020: unresolved token (0A000012) "extern "C" enum CURLcode __clrcall curl_easy_setopt(void *,enum CURLoption,...)" (?curl_easy_setopt@@$$J0YM?AW4CURLcode@@PAXW4CURLoption@@ZZ)
1>333.obj : error LNK2001: unresolved external symbol "extern "C" enum CURLcode __clrcall curl_easy_setopt(void *,enum CURLoption,...)" (?curl_easy_setopt@@$$J0YM?AW4CURLcode@@PAXW4CURLoption@@ZZ)
1>C:\Users\Администратор\documents\visual studio 2010\Projects\333\Debug\333.exe : fatal error LNK1120: 3 unresolved externals
1>
1>Build FAILED.
1>
1>Time Elapsed 00:00:00.87
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

// 333.cpp : main project file.
 
#include "stdafx.h"
#include "Form1.h"
#pragma comment(lib,"curllib.lib")
#include "curl.h"
 
using namespace My333;
 
[STAThreadAttribute]
int main(array<System::String ^> ^args)
{
    // Enabling Windows XP visual effects before any controls are created
    Application::EnableVisualStyles();
    Application::SetCompatibleTextRenderingDefault(false); 
 
    // Create the main window and run it
    Application::Run(gcnew Form1());
    return 0;
}

#pragma once
#pragma comment(lib,"curllib.lib")
#include "curl.h"
 
namespace My333 {
 
    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 Form1
    /// </summary>
    public ref class Form1 : public System::Windows::Forms::Form
    {
    public:
        Form1(void)
        {
            InitializeComponent();
            //
            //TODO: Add the constructor code here
            //
        }
 
    protected:
        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        ~Form1()
        {
            if (components)
            {
                delete components;
            }
        }
    private: System::Windows::Forms::Button^  button1;
    protected: 
 
    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->button1 = (gcnew System::Windows::Forms::Button());
            this->SuspendLayout();
            // 
            // button1
            // 
            this->button1->Location = System::Drawing::Point(102, 238);
            this->button1->Name = L"button1";
            this->button1->Size = System::Drawing::Size(75, 23);
            this->button1->TabIndex = 0;
            this->button1->Text = L"button1";
            this->button1->UseVisualStyleBackColor = true;
            this->button1->Click += gcnew System::EventHandler(this, &Form1::button1_Click);
            // 
            // Form1
            // 
            this->AutoScaleDimensions = System::Drawing::SizeF(6, 13);
            this->AutoScaleMode = System::Windows::Forms::AutoScaleMode::Font;
            this->ClientSize = System::Drawing::Size(292, 273);
            this->Controls->Add(this->button1);
            this->Name = L"Form1";
            this->Text = L"Form1";
            this->ResumeLayout(false);
 
        }
#pragma endregion
    private: System::Void button1_Click(System::Object^  sender, System::EventArgs^  e) {
CURL *curl_handle;
    CURLcode res;
    CURL *curl_easy_init();
    if(curl_handle)
        {
             curl_easy_setopt(curl_handle, CURLOPT_URL, "http://example.com");
            
        }
     
             }
    };
}