how to update in edit a textbox

<asp:TextBox ID="TextBox1" runat="server"> retrival data fro sql</asp:TextBox>
     <br />
     <asp:Button ID="Button1" runat="server" Text="Button" />

protected void Button1_Click(object sender, EventArgs e)
  {
      string str_id = cell_id.InnerText.ToString();

      sqlcon.Open();
      SqlCommand sqlcom = new SqlCommand("updata tableName set colum name where id='"+str_id+"'", sqlcon);
      sqlcom.ExecuteNonQuery();
      sqlcon.Close();

  }