How to Use Three Tier Architecture in SharePoint 2013 Visual WebPart

 SharePoint 2013 List Back end

Ascx Page 

<%@ Assembly Name="$SharePoint.Project.AssemblyFullName$" %>

<%@ Assembly Name="Microsoft.Web.CommandUI, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

<%@ Register Tagprefix="SharePoint" Namespace="Microsoft.SharePoint.WebControls"Assembly="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

<%@ Register Tagprefix="Utilities" Namespace="Microsoft.SharePoint.Utilities"Assembly="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

<%@ Register Tagprefix="asp" Namespace="System.Web.UI" Assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" %>

<%@ Import Namespace="Microsoft.SharePoint" %>

<%@ Register Tagprefix="WebPartPages" Namespace="Microsoft.SharePoint.WebPartPages"Assembly="Microsoft.SharePoint, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c" %>

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="ThreeLayesr.ascx.cs"Inherits="ThreeLayesr.ThreeLayesr.ThreeLayesr" %>

<table cellpadding="0" cellspacing="0" align="center">

    <tr><td colspan="2" align="center"></td></tr>

    <tr><td>Enter UserName</td><td>

        <asp:TextBox ID="txtUserName" runat="server"></asp:TextBox>

        </td></tr>

    <tr><td>Enter PassWord</td><td>

        <asp:TextBox ID="txtPassWord" runat="server"></asp:TextBox>

        </td></tr>

    <tr><td colspan="2" align="center">

        <asp:Button ID="btnSave" runat="server" Text="Save Record" OnClick="btnSave_Click" />

        </td></tr>

</table>

  Ascx.Cs

using System;

using System.ComponentModel;

using System.Web.UI.WebControls.WebParts;

namespace ThreeLayesr.ThreeLayesr

{

    [ToolboxItemAttribute(false)]

    public partial class ThreeLayesr : WebPart

    {

        // Uncomment the following SecurityPermission attribute only when doing Performance Profiling on a farm solution

        // using the Instrumentation method, and then remove the SecurityPermission attribute when the code is ready

        // for production. Because the SecurityPermission attribute bypasses the security check for callers of

        // your constructor, it's not recommended for production purposes.

        // [System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityAction.Assert, UnmanagedCode = true)]

        DataBase db = new DataBase();

        public ThreeLayesr()

        {

        }

        protected override void OnInit(EventArgs e)

        {

            base.OnInit(e);

            InitializeControl();

        }

        protected void Page_Load(object sender, EventArgs e)

        {

        }

        protected void btnSave_Click(object sender, EventArgs e)

        {

            EntityClass obj=new EntityClass();

            obj.strUserName = txtUserName.Text;

            obj.strPassWord = txtPassWord.Text;

            db.InsertSample(obj.strUserName, obj.strPassWord);

            Page.Response.Write("Insertion Successful");

        }

    }

}

Business Layer CS File

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace ThreeLayesr

{

    public class EntityClass

    {

        string UserName;

        string PassWord;

        public string strUserName

        {

            get

            {

                return UserName;

            }

            set

            {

                UserName = value;

            }

        }

        public string strPassWord

        {

            get

            {

                return PassWord;

            }

            set

            {

                PassWord = value;

            }

        }

    }

}

Database Layer CS File

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using Microsoft.SharePoint;

using System.Security;

namespace ThreeLayesr

{

    public class DataBase

    {

       

        public void InsertSample(string strUserName, string strPassWord)

        {

            SPListItemCollection myColl = SPContext.Current.Web.Lists["Login"].Items;

            SPListItem item = myColl.Add();

            item["Title"] = strUserName;

            item["PassWord"] = strPassWord;

            item.Update();

        }

    }

}