help me

using System;
using System. Collections.Generic;
using System. ComponentModel;
using System. Data;
using System. Drawing;
using System. Linq;
using System. Text;
using System. Windows.Forms;

namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
string Kullanici;

string sifre;

Kullanici = textBox1.Text;

sifre = textBox2.Text;

if (Kullanici

"MERT" && sifre

"ER")

textBox3.Text = ("HELAL KANKA DOĞRU GiRDiN");

else

textBox3.Text = ("YANLIŞ GiRDiN KANKA DÜZELT");