C# ve SQL

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

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

private void btnYazma_Click(object sender, EventArgs e)
{
StreamWriter SR = new StreamWriter("C:\\deneme.txt");
SR.WriteLine(textBox1.Text);
SR.Close();
textBox1.Text = "";
MessageBox.Show("Dosyaya Yazıldı");
label1.Visible = true;
label1.Text = "Eklendi";
}

private void btnOkuma_Click(object sender, EventArgs e)
{
StreamReader DR = new StreamReader("C:\\deneme.txt");
string s = DR.ReadLine();
richTextBox1.Text = s;
DR.Close();
}

private void btnEkleme_Click(object sender, EventArgs e)
{
StreamWriter sr = File.AppendText("C:\\deneme.txt");
sr.WriteLine(textBox1.Text);
sr.Close();
textBox1.Text = "";
MessageBox.Show("Dosyaya ekleme yaptın");

}

private void btnVeri_Click(object sender, EventArgs e)
{
StreamReader sr = new StreamReader("C:\\deneme.txt");
//string yazi = sr.ReadToEnd();
////richTextBox1.Text = yazi;
////sr.Close();
string metin = sr.ReadLine();
while (metin != null)
{
richTextBox1.Text = richTextBox1.Text + "\n" + metin;
metin = sr.ReadLine();

}

}

private void Form1_Load(object sender, EventArgs e)
{

}

//private void btnTemizleme_Click(object sender, EventArgs e)
//{
//    System.IO.File.Delete("C\\deneme.txt");
//}
}
}