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.Xml;

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

private void Form1_Load(object sender, EventArgs e)
{

}

private void button1_Click(object sender, EventArgs e)
{
DataSet myDoviz = new DataSet();
myDoviz.ReadXml(
"http://www.tcmb.gov.tr/kurlar/today.xml");
dataGridView1.DataSource = myDoviz.Tables[1];

MessageBox.Show("Dolar : " + dataGridView1.Rows[0].Cells["BanknoteBuying"].Value.ToString());

}

private void button2_Click(object sender, EventArgs e)
{
XmlDocument myDoc = new XmlDocument();
XmlElement myElement ;
//myDoc.Load("http://www.tcmb.gov.tr/kurlar/today.xml");
myDoc.Load(@"a.xml");

MessageBox.Show("Kökte : " + myDoc.ChildNodes.Count.ToString()
+" node var");

MessageBox.Show("İlk Hiyerarşi : " + myDoc.ChildNodes[1].Name);
MessageBox.Show("İlk Hiyerarşinin altında  : "
+ myDoc.ChildNodes[1].ChildNodes.Count.ToString());

MessageBox.Show(
myDoc.
ChildNodes[1].
ChildNodes[0].
ChildNodes[1].
Attributes[0].Value.ToString());

}

private void button3_Click(object sender, EventArgs e)
{
XmlDocument myDoc = new XmlDocument();
XmlElement myElement;
myDoc.Load(@"a.xml");
for (int i = 0; i < myDoc.ChildNodes.Count; i++)
{
try
{
textBox1.Text = textBox1.Text + myDoc.ChildNodes[i].Value.ToString();
}
catch { }
if(myDoc.ChildNodes[i].HasChildNodes)
{
for (int j = 0; j < myDoc.ChildNodes[i].ChildNodes.Count; j++)
{
try
{
textBox1.Text = textBox1.Text + myDoc.ChildNodes[i].ChildNodes[j].Value.ToString();
}
catch { }
}
}

}

}
}
}