Retrieving data from database into textbox

<asp:TextBox ID="TextBox6" runat="server"></asp:TextBox><br />

<asp:Button ID="Button1" runat="server" Text="Retrive data"

onclick="Button1_Click" />

<asp:Label ID="lbl1" runat="server" BackColor="Black" Font-Bold="True"

ForeColor="Red"></asp:Label>

</div>

</form>

</body>

</html>

using System;

using System.Configuration;

using System.Data;

using System.Linq;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.HtmlControls;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Xml.Linq;

using System.Data.SqlClient;

public partial class _Default : System.Web.UI.Page

{

string connStr = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;

SqlCommand com;

string str;

protected void Button1_Click(object sender, EventArgs e)

{

clear();

idcheck();

SqlConnection con = new SqlConnection(connStr);

con.Open();

str = "select * from std where REGDNO='" + TextBox1.Text.Trim() + "'";

com = new SqlCommand(str, con);

SqlDataReader reader = com.ExecuteReader();

if (reader.Read())

{

TextBox2.Text =reader["NAME"].ToString();

TextBox3.Text = reader["BRANCH"].ToString();

TextBox4.Text = reader["ADDRESS"].ToString();

TextBox5.Text = reader["PHNO"].ToString();

TextBox6.Text = reader["STATE"].ToString();

reader.Close();

con.Close();

}

}

public void idcheck()

{

SqlConnection con = new SqlConnection(connStr);

con.Open();

str = "select count(*)from std where REGDNO='" + TextBox1.Text + "'";

com = new SqlCommand(str, con);

int count = Convert.ToInt32(com.ExecuteScalar());

if (count > 0)

{

lbl1.Text = "Id Exist";

}

else

{

lbl1.Text = "Id Does not Exist";

}

}

void clear()

{

TextBox2.Text = "";

TextBox3.Text = "";

TextBox4.Text = "";

TextBox5.Text = "";

TextBox6.Text = "";

}

}