first usercontrol event firing well but for second onwards it needs double click why please help me

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ASP.NET

Here is my DynamicUserControl.Aspx code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class DynamicUserControl : System.Web.UI.Page
{
    //UserControl_WebUserControl1 ucSimpleControl;
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            Session["test"] = null;
        }
        int id = 1;
        
        if (Session["test"] != null)
        {
           
            id = int.Parse(Session["test"].ToString());
        
        }
        if (Session["test"] == null)
        {
            UserControl_WebUserControl1 ucSimpleControl = (UserControl_WebUserControl1)LoadControl("~/UserControl/WebUserControl" + id + ".ascx");
            ControlHolder.Controls.Clear();
            ControlHolder.Controls.Add(ucSimpleControl);

            ucSimpleControl.Next1Click += new EventHandler(ucSimpleControl_Next1Click);
        }
        if (id == 2)
        {
            UserControl_WebUserControl2 ucSimpleControl = (UserControl_WebUserControl2)LoadControl("~/UserControl/WebUserControl" + id + ".ascx");
            ControlHolder.Controls.Clear();
            ControlHolder.Controls.Add(ucSimpleControl);

            ucSimpleControl.Next2Click += new EventHandler(ucSimpleControl_Next2Click);
        }
        if (id == 3)
        {
            UserControl_WebUserControl3 ucSimpleControl = (UserControl_WebUserControl3)LoadControl("~/UserControl/WebUserControl" + id + ".ascx");
            ControlHolder.Controls.Clear();
            ControlHolder.Controls.Add(ucSimpleControl);

            ucSimpleControl.Next3Click += new EventHandler(ucSimpleControl_Next3Click);
        }
            
             //ucSimpleControl = (UserControl_WebUserControl1)LoadControl("~/UserControl/WebUserControl"+id+".ascx");
            
        

    }
    
    protected void ucSimpleControl_Next1Click(object sender, EventArgs e)
    {
        Response.Write("It's working");
    }

    protected void ucSimpleControl_Next2Click(object sender, EventArgs e)
    {
        Response.Write("It's working");
    }
    protected void ucSimpleControl_Next3Click(object sender, EventArgs e)
    {
        Response.Write("It's working");
    }
   
}

My FirstUsercontrol.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;


    public partial class UserControl_WebUserControl1 : System.Web.UI.UserControl
    {
        public event EventHandler Next1Click;

        protected void Page_Load(object sender, EventArgs e)
        {
            Session["test"] = null;
        }
        protected void Next1_Click(object sender, EventArgs e)
        { 
            Session["test"] = "2";

            UserControl_WebUserControl2 ucSimpleControl = (UserControl_WebUserControl2)LoadControl("~/UserControl/WebUserControl2.ascx");

            PlaceHolder phContactDetails = (PlaceHolder)Page.FindControl("ControlHolder");
            phContactDetails.Controls.Clear();
            phContactDetails.Controls.Add(ucSimpleControl);
            ucSimpleControl.Next2Click += new EventHandler(ucSimpleControl_Next2Click);
          
        }

        protected void ucSimpleControl_Next2Click(object sender, EventArgs e)
        {
            Response.Write("It's working");
        }
    }

my second usercontrol.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
  public partial class UserControl_WebUserControl2 : System.Web.UI.UserControl
    {
        public event EventHandler Next2Click;
        protected void Page_Load(object sender, EventArgs e)
        {

        }
        protected void Next2_Click(object sender, EventArgs e)
        { 
            Session["test"] = "3";
            UserControl_WebUserControl3 ucSimpleControl = (UserControl_WebUserControl3)LoadControl("~/UserControl/WebUserControl3.ascx");

            PlaceHolder phContactDetails = (PlaceHolder)Page.FindControl("ControlHolder");
            phContactDetails.Controls.Clear();
            phContactDetails.Controls.Add(ucSimpleControl);
            ucSimpleControl.Next3Click += new EventHandler(ucSimpleControl_Next3Click);
           
        }
        protected void ucSimpleControl_Next3Click(object sender, EventArgs e)
        {
            Response.Write("It's working");
        }
    }

my third usercontrol.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;


    public partial class UserControl_WebUserControl3 : System.Web.UI.UserControl
    {
        public event EventHandler Next3Click;
        protected void Page_Load(object sender, EventArgs e)
        {

        }
        protected void Next3_Click(object sender, EventArgs e)
        {
            Next3Click(sender, e);
            //PlaceHolder phContactDetails = new PlaceHolder();
            //phContactDetails.Controls.Add(LoadControl("~/UserControl/WebUserControl3.ascx"));
        }
        protected void UserControl_WebUserControl1_Next3Click(object sender, EventArgs e)
        {
            Response.Write("It's working fine");
        }
    }

please help me why from second user control we have to click the button twice for firing next button events.
Thanks in Advance.

[edit]Code blocks added - OriginalGriff[/edit]