Image handler not reloading my image! Or my defualt image .

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hello
im using handlers to do upload edit delete images its work just fine ! but when i delete and set a defualt image dosnot show up until i refresh the page !

What I have tried:

C#

public class Handler1 : IHttpHandler, IRequiresSessionState
    {
        public static string strCon = System.Configuration.ConfigurationManager.AppSettings["connectionstring"];
        public void ProcessRequest(HttpContext context)
        {
            SqlConnection _con = new SqlConnection(strCon);
            var id = context.Request.Params.GetValues("id");
            int ImgNumber = Convert.ToInt32(id[0].ToString());
            int wasteCheckID = Convert.ToInt32(context.Session["WasteCheckID"]);
            string stDelete = "DELETE FROM tbl_LogisticsWasteCheckImg WHERE WasteCheckID=" + wasteCheckID + " AND ImgNumber=" + ImgNumber;
            SqlCommand cmdDelete = new SqlCommand(stDelete, _con);
            _con.Open();
            cmdDelete.ExecuteNonQuery();
            _con.Close();
            string strget = "select img from tbl_logisticswastecheckimg where wastecheckid=114  and imgnumber=1";
            _con.Open();
            using (SqlDataAdapter sda = new SqlDataAdapter(strget, _con))
            {
                DataTable dt = new DataTable();
                sda.Fill(dt);
                if (dt.Rows.Count > 0)
                {
                    byte[] bytes = (byte[])dt.Rows[0]["img"];
                    context.Response.BinaryWrite(bytes);

                    context.Response.End();
                }
                else
                {
                    context.Response.WriteFile("~/images/a.png");
                    //read image file into image object.
                    Image img = Image.FromFile(context.Server.MapPath("~/images/a.png"));

                    //imageconverter class convert image object to byte array.
                    byte[] bytes = (byte[])(new ImageConverter()).ConvertTo(img, typeof(byte[]));
                    context.Response.BinaryWrite(bytes);
                    context.Response.End();
                }
            }
        }
        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }
}

Posted 11-Oct-18 0:25am

Member 13990122

Updated 14-Oct-18 20:43pm

Bryian Tan

v2

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Comments

Richard Deeming 11-Oct-18 9:01am

"DELETE FROM tbl_LogisticsWasteCheckImg WHERE WasteCheckID=" + wasteCheckID + " AND ImgNumber=" + ImgNumber

Don't do it like that!

In this specific case, since both parameters are integers, you should be OK. But using string concatenation to build a SQL query can and will lead to SQL Injection vulnerabilities. Always use a parameterized query instead.

const string stDelete = "DELETE FROM tbl_LogisticsWasteCheckImg WHERE WasteCheckID = @WasteCheckID AND ImgNumber = @ImgNumber";
using (SqlCommand cmdDelete = new SqlCommand(strDelete, _con))
{
    cmdDelete.Parameters.AddWithValue("@WasteCheckID", wasteCheckID);
    cmdDelete.Parameters.AddWithValue("@ImgNumber", ImgNumber);
    
    _con.Open();
    cmdDelete.ExecuteNonQuery();
    _con.Close();
}

Everything you wanted to know about SQL injection (but were afraid to ask) | Troy Hunt[^]
How can I explain SQL injection without technical jargon? | Information Security Stack Exchange[^]
Query Parameterization Cheat Sheet | OWASP[^]

Member 13990122 15-Oct-18 2:40am

hi
Thanks , yes i know a bit about it :) but thanks agian ,

2 solutions

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Vincent Maverick Durano · Answer 1 · 2018-10-11T05:12:00

Solution 1

That's probably because the browser is caching the image. If you want to make sure the browser refreshes the image you can either:

(1) Add the appropriate Cache headers.

C#

HttpResponse Response = HttpContext.Current.Response;
Response.Expires = 0;
Response.Cache.SetCacheability(HttpCacheability.NoCache);

(2) Add a unique query string to the URL to force a refresh.

C#

Image1.ImageUrl = "~/images/a.png"+"?" + DateTime.Now.Ticks;

Posted 11-Oct-18 5:12am

Vincent Maverick Durano

Comments

Member 13990122 15-Oct-18 2:43am

hi ,
i tried to clear the cache, but the same problem ! add unique query string is hard due i send the ID as static.
. i call image bumber 1 !

Member 13990122 15-Oct-18 2:47am

i have the code in the comment after.

Vincent Maverick Durano 15-Oct-18 10:49am

You could still use the static ID. The idea is to append the DateTime.Now.Ticks to to the URL so it will force a browser refresh.

Member 13990122 · Answer 2 · 2018-10-14T20:43:00

Solution 2

<pre><img id="Img1" runat="server" src='~/Get.ashx?imgID=1' class="img" />

Posted 14-Oct-18 20:43pm

Member 13990122