gridview search

hi every body I have grid view where I need to make search in the first cell the other cells in the same row autocomplete on first cell search I can only edit

quantity number and jumped to the second row to search for anew product and so on My problem happened when I return back to edit quantity in any previous row and try to add new product it repeat data in row edited or happened when I use arrows

this is my form where is the problem I need to know how to solve this problem and why it happened

http://www.mediafire.com/download/cweih3zc4pth4xi/Market+2.zip

SqlConnection con = new SqlConnection("yourconnstring");

private void button5_Click(object sender, EventArgs e)

{

con.Open();

SqlCommand cmd = con.CreateCommand();

cmd.CommandType = CommandType.Text;

cmd.CommandText = "Select * from table1 where name='"+textBox1.Text+"'";

cmd.ExecuteNonQuery();

DataTable dt = new DataTable();

SqlDataAdapter da = new SqlDataAdapter(cmd);

da.Fill(dt);

dataGridView1.DataSource = dt;

con.Close();

}

private void dataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)

{

if (e.RowIndex >= 0)

{

DataGridViewRow row=this.dataGridView1.Rows [e.RowIndex];

textBox1.Text = row.Cells["Name"].Value.ToString();

textBox1.ReadOnly = true;

textBox2.Text = row.Cells["ID"].Value.ToString();

textBox1.ReadOnly = true;

textBox3.Text = row.Cells["Age"].Value.ToString();

}