3 tier architecture example in asp.net with C#

ASPX page

<table>
        <tr>
            <td colspan="2">
                <asp:Label ID="lblMsg" runat="server" Text="" ForeColor="Red"></asp:Label>
            </td>
        </tr>
        <tr>
            <td>
                Name :
            </td>
            <td>
                <asp:TextBox ID="txtName" runat="server"></asp:TextBox>
            </td>
        </tr>
        <tr>
            <td>
                <asp:Button ID="btnAdd" runat="server" Text="Add" OnClick="btnAdd_Click" />
            </td>
            <td>
                <asp:Button ID="btnBack" runat="server" Text="Back" />
            </td>
        </tr>
    </table>

**************************************************************************

cs file of aspx page


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;

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

    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void btnAdd_Click(object sender, EventArgs e)
    {
//call class file here
        Datatbl objData = new Datatbl();
        objData.tblId = "";
        objData.tblName = txtName.Text;

        DAOtbl objDAO = new DAOtbl();
        objDAO.insert(objData);
    }
}

*****************************************************************
now add class file Datatbl.cs



using System;
using System.Data;
using System.Configuration;
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;

public class Datatbl
{
    private string id;
    private string name;

    public string tblId
    {
        get
        {
            return id;
        }
        set
        {
            id = value;
        }
    }

    public string tblName
    {
        get
        {
            return name;
        }
        set
        {
            name = value;
        }
    }
}

*************************************************************************
Now Establish connection Database.cs



using System;
using System.Data;
using System.Configuration;
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 class Database
{
    public static SqlConnection connect()
    {
        SqlConnection con1 = new SqlConnection();
        con1.ConnectionString = "Data Source=.\\SQLExpress;AttachDbFileName=|DataDirectory|Database1.mdf;Integrated Security=True;User Instance=True;";
        return con1;
    }
}



*****************************************************************

Logic of get data,delete,update DAOtbl.cs


using System;
using System.Data;
using System.Configuration;
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 class DAOtbl
{
    SqlConnection con = null;
    SqlCommand cmd = null;
    SqlDataAdapter adp = null;
    DataTable dt = null;
    string query = "";

    public Boolean isDuplicate(string name)
    {
        query = "SELECT COUNT(*) FROM tbl WHERE Name=@Name";
        con = Database.connect();
        cmd = new SqlCommand(query, con);
        cmd.Parameters.AddWithValue("@Name", name);

        con.Open();
        int count = Convert.ToInt16(cmd.ExecuteScalar());
        con.Close();
        if (count == 0)
            return false;
        return true;
    }

    public Boolean insert(Datatbl obj)
    {
        query = "INSERT INTO tbl VALUES (@Name)";
        con = Database.connect();
        cmd = new SqlCommand(query, con);
        cmd.Parameters.AddWithValue("@Name", obj.tblName);

        con.Open();
        int noOfRowsAffected = cmd.ExecuteNonQuery();
        con.Close();

        if (noOfRowsAffected == 1)
            return true;
        return false;
    }

    public Boolean update(Datatbl obj)
    {
        query = "UPDATE tbl SET Name=@Name WHERE Id=@Id";
        con = Database.connect();
        cmd = new SqlCommand(query, con);
        cmd.Parameters.AddWithValue("@Id", obj.tblId);
        cmd.Parameters.AddWithValue("@Name", obj.tblName);

        con.Open();
        int noOfRowsAffected = cmd.ExecuteNonQuery();
        con.Close();

        if (noOfRowsAffected == 1)
            return true;
        return false;
    }

    public Boolean delete(string id)
    {
        query = "DELETE FROM tbl WHERE Id=@Id";
        con = Database.connect();
        cmd = new SqlCommand(query, con);
        cmd.Parameters.AddWithValue("@Id", id);

        con.Open();
        int noOfRowsAffected = cmd.ExecuteNonQuery();
        con.Close();

        if (noOfRowsAffected == 1)
            return true;
        return false;
    }

    public Datatbl getDataById(string id)
    {
        query = "SELECT * FROM tbl WHERE Id=@Id";
        con = Database.connect();
        cmd = new SqlCommand(query, con);
        cmd.Parameters.AddWithValue("@Id", id);

        dt = new DataTable();
        adp = new SqlDataAdapter(cmd);

        con.Open();
        adp.Fill(dt);
        con.Close();

        Datatbl dataObj = null;
        if (dt != null && dt.Rows.Count == 1)
        {
            dataObj = new Datatbl();
            dataObj.tblId = dt.Rows[0]["Id"].ToString();
            dataObj.tblName = dt.Rows[0]["Name"].ToString();
        }
        return dataObj;
    }

    public DataTable getData()
    {
        query = "SELECT * FROM tbl";
        con = Database.connect();
        cmd = new SqlCommand(query, con);
        dt = new DataTable();
        adp = new SqlDataAdapter(cmd);

        con.Open();
        adp.Fill(dt);
        con.Close();

        return dt;
    }
}