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Refer the sample.

Database

HTML

ArticleTitle

<div class="" style="width: 100%; margin: 0 auto; color: #011b33; padding: 10px;">
    <div class="col-sm-11" style="margin: 0 auto; padding: 10px; width: 100%;">
        <label style="color: #00003D;">Articles</label>
    </div>
    <div class="col-sm-10" style="margin: 0 auto; padding: 6px;">
        <asp:Repeater ID="rptPages" runat="server">
            <ItemTemplate>
                <%# Container.ItemIndex + 1 %>.&nbsp;
                <asp:HyperLink ID="HyperLink2" NavigateUrl='<%# string.Format("~/contents/{0}/{1}.aspx", Eval("ArticleId"), Eval("Slug")) %>'
                    Text='<%# Eval("Title") %>' runat="server" />
            </ItemTemplate>
            <SeparatorTemplate>
                <br />
            </SeparatorTemplate>
        </asp:Repeater>
    </div>
</div>

Articlecontents

<div class="" style="width: 100%; margin: 0 auto; color: #011b33; padding: 10px;">
    <div class="col-sm-11" style="margin: 0 auto; padding: 10px; width: 100%;">
        <label style="color: #00003D;">Detailed contents</label>
    </div>
    <div class="col-sm-10" style="margin: 0 auto; padding: 6px;">
        <h5>
            <asp:Label ID="lblTitle" runat="server" Text="Title" />
            <%--<asp:Label ID="timelbl" runat="server" Text="" Font-Size="Smaller" Font-Bold="true"></asp:Label>--%>
        </h5>
        <hr />
        <asp:Label ID="lblBody" runat="server" Text="Body" />
    </div>
</div>

Namespaces

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

Code

ArticleTitle

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.PopulateArticleId();
    }
}
private void PopulateArticleId()
{
    string query = "SELECT [ArticleId], [Title], REPLACE([Title], ' ', '-') [SLUG], [Body] FROM [Blogs]";
    using (SqlConnection con = new SqlConnection(@"server=.;DataBase=AjaxSamples;UID=sa;PWD=pass@123;"))
    {
        using (SqlCommand cmd = new SqlCommand(query))
        {
            using (SqlDataAdapter sda = new SqlDataAdapter())
            {
                cmd.Connection = con;
                sda.SelectCommand = cmd;
                using (DataTable dt = new DataTable())
                {
                    sda.Fill(dt);
                    rptPages.DataSource = dt;
                    rptPages.DataBind();
                }
            }
        }
    }
}

Articlecontents

public partial class Articlecontents : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            this.PopulateArticle();
        }
    }
    private void PopulateArticle()
    {
        string articleId = this.Page.RouteData.Values["ArticleId"].ToString();
        string query = "SELECT [Title], [Body] FROM [Blogs] WHERE [ArticleId] = @ArticleId";
        using (SqlConnection con = new SqlConnection(@"server=.;DataBase=AjaxSamples;UID=sa;PWD=pass@123;"))
        {
            using (SqlCommand cmd = new SqlCommand(query))
            {
                using (SqlDataAdapter sda = new SqlDataAdapter())
                {
                    cmd.Parameters.AddWithValue("@ArticleId", articleId);
                    cmd.Connection = con;
                    sda.SelectCommand = cmd;
                    using (DataTable dt = new DataTable())
                    {
                        sda.Fill(dt);
                        lblTitle.Text = dt.Rows[0]["Title"].ToString();
                        lblBody.Text = dt.Rows[0]["Body"].ToString();
                        //timelbl.Text = dt.Rows[0]["DatePosted"].ToString();
                    }
                }
            }
        }
    }
}

Global

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Routing;
using System.Web.Security;
using System.Web.SessionState;

namespace Article_On_Website
{
    public class Global : System.Web.HttpApplication
    {
        protected void Application_Start(object sender, EventArgs e)
        {
            RegisterRoutes(RouteTable.Routes);
        }

        static void RegisterRoutes(RouteCollection routes)
        {
            routes.MapPageRoute("Articlecontents", "contents/{ArticleId}/{Slug}.aspx", "~/Articlecontents.aspx");
        }
    }
}

Screenshot

dharmendr says:

What issue you are facing now?

Ths mistake I did was that I added the extension (.aspx) to the route in Global file.

routes.MapPageRoute("DisplayArticles", "Articles/{ArticleId}/{Slug}.aspx", "~/DisplayArticles.aspx"); 

So when I removed the extension (.aspx), it worked. This is my correct routing in Global file

 routes.MapPageRoute("DisplayArticles", "Articles/{ArticleId}/{Slug}", "~/DisplayArticles.aspx");