Displaying Binary PDF file on a webpage using Generic Handler

Question

Displaying Binary PDF file on a webpage using Generic Handler

Donald Symmons 3,066

In my old Visual Studio, I was able to retrieve and display a pdf file saved in the database but in this latest visual studio the file does not display, any help in displaying it please? HTML

<div class="contentt">     
	<asp:Literal ID="ltEmbed" runat="server" />
</div>

C#

 protected void Page_Load(object sender, EventArgs e)
        {
            FileDisplay();
        }

 private void FileDisplay()
        {
            if (Request.QueryString["Id"] != null)
            {
                int id = Convert.ToInt32(Request.QueryString["Id"]);
                // Binding PDF file in Literal control
               string embed = "<object data=\"{0}{1}\" type=\"application/pdf\" width=\"500px\" height=\"650px\"></object>";
               ltEmbed.Text = string.Format(embed, ResolveUrl("~/Handler1.ashx?Id="), id);
            }
        }

Generic Handler (Handler.ashx) In this Generic Handler, I noticed that it is Handler1.ashx.cs, but in the old version of Visual Studio, it is Handler1.ashx, I don't know if this could result to difference in code.

using System;
using System.Web;
using System.Data.SqlClient;

public class Handler1 : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            int id = int.Parse(context.Request.QueryString["Id"]);
            byte[] bytes;
            string contentType;
            using (SqlConnection con = new SqlConnection())
            {
                using (SqlCommand cmd = new SqlCommand())
                {
                    cmd.CommandText = "SELECT Data, contentType FROM FileTable WHERE Id=@Id";
                    cmd.Parameters.AddWithValue("@Id", id);
                    cmd.Connection = con;
                    con.Open();
                    using (SqlDataReader sdr = cmd.ExecuteReader())
                    {
                        sdr.Read();
                        bytes = (byte[])sdr["Data"];
                        contentType = sdr["contentType"].ToString();
                    }
                    con.Close();
                }
            }

             context.Response.Buffer = true;
            context.Response.Charset = "";
            context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
            context.Response.ContentType = "application/pdf";
            context.Response.BinaryWrite(bytes);
            context.Response.Flush();
            context.Response.End();
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }

Accepted answer

1 additional answer

Your answer

Answer 1

Please use an iframe instead of the Literal control and set the url of HTTP handler to the src attribute of iframe.

See sample below:

HTTP Handler Handler4.ashx

using System;
using System.Web;

namespace WebForms1
{
    public class Handler4 : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
            context.Response.Cache.SetExpires(DateTime.Now.ToUniversalTime());
            context.Response.Cache.SetMaxAge(new TimeSpan(0, 0, 0, 0));
            context.Response.ContentType = "application/pdf";

            // byte array is obtained from the file in Files holder (not from DB)
            string filename = "JBL4312G.pdf";
            string path = context.Server.MapPath("~/Files") + "\\" + filename;
            byte[] data = System.IO.File.ReadAllBytes(path);

            context.Response.BinaryWrite(data);
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}

.aspx

<%@ Page Language="C#" AutoEventWireup="true" 
    CodeBehind="WebForm33.aspx.cs" Inherits="WebForms1.WebForm33" %>

<!DOCTYPE html>

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
        <h1>pdf in iframe</h1>
        <iframe src="Handler4.ashx" width="500" height="500"></iframe>
    </form>    
</body>
</html>

result

enter image description here

Donald Symmons 3,066 Reputation points

2024-01-26T02:51:37.2566667+00:00

Hi @SurferOnWww ,

Please use an iframe instead of the Literal control and set the url of HTTP handler to the src attribute of iframe.

How please? Can you give a little example to demonstrate. I haven't used an iframe before
Donald Symmons 3,066 Reputation points

2024-01-26T04:35:31.8233333+00:00

Hi @SurferOnWww ,

I later figured it out. Oh! I just saw you gave me an example, but I'd already done it before seeing your example, and it worked. Thank you

Answer 2

Lan Huang-MSFT 30,186 Microsoft External Staff

Hi @Donald Symmons,

I found a workaround where you can change back to Handler1.ashx.

add a Generic handler - Handler1.ashx in visual studio
delete the cs file which auto-created.
open ashx again,
- remove CodeBehind="Handler1.ashx.cs"
- add c# code below
Best regards,
Lan Huang

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Donald Symmons 3,066 Reputation points

2024-01-26T02:48:53.13+00:00

Hi @Lan Huang-MSFT ,

I did exactly like you told me to, but it did not display the file. No errors were shown in the code but I don't know why it did not display.

You can see from the image above, other information regarding the file displayed at the right of the image, but the pdf file which is suppose to show in the area surrounded by the red line, did not display.
Lan Huang-MSFT 30,186 Reputation points Microsoft External Staff

2024-01-26T03:40:39.68+00:00

Hi @Donald Symmons, Your problem seems to be because you are not connected to the database.
SurferOnWww 4,631 Reputation points

2024-01-26T03:56:07.8766667+00:00

You cannot show the content of pdf on the Literal control no matter how you modify the HTTP handler. As I answered use an iframe instead of the Literal control.

Donald Symmons 3,066

Hi @SurferOnWww , This is what I tried. HTML

<iframe runat="server" id="iframepdf" height="700" width="500"></iframe>

C#

 private void FileDisplay()
        {
            if (Request.QueryString["Id"] != null)
            {
                int id = Convert.ToInt32(Request.QueryString["Id"]);
                // Binding PDF file in Literal control
                iframepdf.Attributes["src"] = ResolveUrl("~/Admin/Handler1.ashx?Id=" + id);
            }
        }

Generic Handler.ashx

<%@ WebHandler Language="C#" Class="Handler1" %>

using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Linq;
using System.Web;
using System.Configuration;

namespace JOSMADE
{
    /// <summary>
    /// Summary description for Handler1
    /// </summary>
    public class Handler1 : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            int id = int.Parse(context.Request.QueryString["Id"]);
            byte[] bytes;
            string contentType;
            string constr = "Data Source=(LocalDB)\\MSSQLLocalDB;AttachDbFilename=C:\\Users\\user\\source\\repos\\JOSMADE\\JOSMADE\\App_Data\\Josmade_QuirverDB.mdf;Integrated Security=True";
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand())
                {
                    cmd.CommandText = "SELECT Data, contentType FROM FileTable WHERE Id=@Id";
                    cmd.Parameters.AddWithValue("@Id", id);
                    cmd.Connection = con;
                    con.Open();
                    using (SqlDataReader sdr = cmd.ExecuteReader())
                    {
                        sdr.Read();
                        bytes = (byte[])sdr["Data"];
                        contentType = sdr["contentType"].ToString();
                    }
                    con.Close();
                }
            }

            context.Response.Buffer = true;
            context.Response.Charset = "";
            context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
            context.Response.ContentType = "application/pdf";
            context.Response.BinaryWrite(bytes);
            context.Response.Flush();
            context.Response.End();
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}

It worked. Thanks

Lan Huang-MSFT 30,186 Microsoft External Staff

You can see from the image above, other information regarding the file displayed at the right of the image, but the pdf file which is suppose to show in the area surrounded by the red line, did not display.

This problem has been solved, but it still needs to be explained. The problem of no display is that ConnectionString is not used to connect to the database and has nothing to do with the Literal control. My Test

 <div class="contentt">
     <asp:Literal ID="ltEmbed" runat="server" />
 </div>

 protected void Page_Load(object sender, EventArgs e)
 {
     FileDisplay();
 }

 private void FileDisplay()
 {

     // if (Request.QueryString["Id"] != null)
     //{
     //int id = Convert.ToInt32(Request.QueryString["Id"]);
     //Test
     int id = 1;
     // Binding PDF file in Literal control
     string embed = "<object data=\"{0}{1}\" type=\"application/pdf\" width=\"500px\" height=\"650px\"></object>";
     ltEmbed.Text = string.Format(embed, ResolveUrl("~/Handler1.ashx?Id="), id);
     // }
 }

<%@ WebHandler Language="C#" Class="WebFormDemo.Handler1" %>

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

namespace WebFormDemo
{
    public class Handler1 : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            int id = int.Parse(context.Request.QueryString["Id"]);
            byte[] bytes;
            string contentType;
            string constr = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand())
                {
                    cmd.CommandText = "SELECT Data, contentType FROM FileTable WHERE Id=@Id";
                    cmd.Parameters.AddWithValue("@Id", id);
                    cmd.Connection = con;
                    con.Open();
                    using (SqlDataReader sdr = cmd.ExecuteReader())
                    {
                        sdr.Read();
                        bytes = (byte[])sdr["Data"];
                        contentType = sdr["contentType"].ToString();
                    }
                    con.Close();
                }
            }

            context.Response.Buffer = true;
            context.Response.Charset = "";
            context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
            context.Response.ContentType = "application/pdf";
            context.Response.BinaryWrite(bytes);
            context.Response.Flush();
            context.Response.End();
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}

User's image

Donald Symmons 3,066

Hi @Lan Huang-MSFT ,

I can see from your example. But could be because my Generic Handler is inside a folder? I have a folder for 'Admin' and that is where I put my Generic Handler is located. So I did this:

 string embed = "<object data=\"{0}{1}\" type=\"application/pdf\"></object>";
 ltEmbed.Text = string.Format(embed, ResolveUrl("~/Admin/Handler1.ashx?Id="), id);

Because in my end, the file still does not display

<%@ WebHandler Language="C#" Class="JOSMADE.Handler1" %>

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

namespace JOSMADE
{
    /// <summary>
    /// Summary description for Handler1
    /// </summary>
    public class Handler1 : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            int id = int.Parse(context.Request.QueryString["Id"]);
            byte[] bytes;
            string contentType;
            string constr = ConfigurationManager.ConnectionStrings["ConString"].ConnectionString;
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand())
                {
                    cmd.CommandText = "SELECT Data, contentType FROM FileTable WHERE Id=@Id";
                    cmd.Parameters.AddWithValue("@Id", id);
                    cmd.Connection = con;
                    con.Open();
                    using (SqlDataReader sdr = cmd.ExecuteReader())
                    {
                        sdr.Read();
                        bytes = (byte[])sdr["Data"];
                        contentType = sdr["contentType"].ToString();
                    }
                    con.Close();
                }
            }

            context.Response.Buffer = true;
            context.Response.Charset = "";
            context.Response.Cache.SetCacheability(HttpCacheability.NoCache);
            context.Response.ContentType = "application/pdf";
            context.Response.BinaryWrite(bytes);
            context.Response.Flush();
            context.Response.End();
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}

Lan Huang-MSFT 30,186 Reputation points Microsoft External Staff

2024-02-02T01:41:43.66+00:00

Hi @Donald Symmons,

Your code will work regardless of whether the universal handler is inside the folder or not.

You need to make sure you are properly connected to the database.

I guess the reason your using <iframe> works is because you added the connectionString in the generic handler.

In my example, you need to configure the connectionString in the Web.config file. I don't know if you have configured it.

You can change your code from

to

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Displaying Binary PDF file on a webpage using Generic Handler

1 additional answer

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