displaying image (from database) in an image control

Question

Triyng to retrieve and display image from database in an image control based on employeeid... I have taken an httphandler in which i have this:

  Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest

    'context.Response.ContentType = "text/plain"
    'context.Response.Write("Hello World!")

    Dim employeeId As Integer
    If (Not (context.Request.QueryString("employeeId")) Is Nothing) Then
        employeeId = Convert.ToInt32(context.Request.QueryString("employeeId"))
    Else
        Throw New ArgumentException("No parameter specified")
    End If
    Dim imageData() As Byte = {}
    ' get the image data from the database using the employeeId Querystring
    context.Response.ContentType = "image/jpeg"
    ' You can retrieve this also from the database
    context.Response.BinaryWrite(imageData)

End Sub

Protected Sub DisplayButton_Click(ByVal sender As Object, ByVal e As EventArgs) Handles DisplayButton.Click
    bind()
    GridView1.Visible = "True"
    ProcessRequest(Context)
End Sub

Error: The 'MasterPageFile' property can only be set in or before the 'Page_PreInit' event. Where am I going wrong? What all changes do i need to make?

This is the image control on the form:

<asp:Image ID="Image1" runat="server" imageUrl="HttpHandler.ashx?employeeId=5"/>

@Stefano Altieri:

This is on Employee.aspx

Protected Sub DisplayButton_Click(ByVal sender As Object, ByVal e As EventArgs) Handles DisplayButton.Click
    bind()
    GridView1.Visible = "True"
    Image1.ImageUrl = "~/HttpHandler.ashx?EmployeeID='" & EmailIDTextBox.Text & "'"
End Sub

and this is on HttpHandler.ashx

Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest

    'context.Response.ContentType = "text/plain"
    'context.Response.Write("Hello World!")

    Dim employeeId As Integer
    If (Not (context.Request.QueryString("employeeId")) Is Nothing) Then
        employeeId = Convert.ToInt32(context.Request.QueryString("employeeId"))
    Else
        Throw New ArgumentException("No parameter specified")
    End If
    Dim imageData() As Byte = {}
    ' get the image data from the database using the employeeId Querystring
    context.Response.ContentType = "image/jpeg"
    ' You can retrieve this also from the database
    context.Response.BinaryWrite(imageData)

End Sub

when i call ProcessRequest (i.e. when it should go to the httphandler (.ashx page)) — who-aditya-nawandar, Mar 04 '13 at 09:44
Also... I am a little confused... is this a page or an http handlers? It can't be both.. you have to implement http handlers in a separate ashx file — Stefano Altieri, Mar 04 '13 at 09:44
Take a look at my answer in this post: http://stackoverflow.com/questions/14935205/retrieve-image-from-database-in-asp-net/14935469#14935469 — Stefano Altieri, Mar 04 '13 at 09:45
i have. i have implemented the handler on an ashx page... the above code is on the employee page on which i have the display button to display employee image... — who-aditya-nawandar, Mar 04 '13 at 09:46
I don't think this will ever work. You have to separate the things and call the handler using the ImageUrl propery of an image. Ie. ImageUrl=GetImage.ashx?employeeId=123 — Stefano Altieri, Mar 04 '13 at 09:47
thats what i am doing there its not working.... the name of my handler is HttpHandler.ashx... hope am explaining it clearly... — who-aditya-nawandar, Mar 04 '13 at 09:50
No, you are mixing page and handler code. Can you post the codes (and the pagne/handler file names? — Stefano Altieri, Mar 04 '13 at 09:59
I have posted the page and handler names with corresponding codes. Now I have this: Error - "Input string was not in a correct format!" — who-aditya-nawandar, Mar 04 '13 at 10:14
Ok,you don't need to quote the id in query string ('" & EmailIDTextBox.Text & "'") — Stefano Altieri, Mar 04 '13 at 10:19
Use: Image1.ImageUrl = "~/HttpHandler.ashx?EmployeeID=" & EmailIDTextBox.Text — Stefano Altieri, Mar 04 '13 at 10:20
As a general hint... can you provide the line where the exception is thrown? — Stefano Altieri, Mar 04 '13 at 10:29
employeeId = Convert.ToInt32(context.Request.QueryString("employeeId")) its the third line in the handler... — who-aditya-nawandar, Mar 04 '13 at 10:36
So the parameter is not an integer! Try using the debugger to see the value — Stefano Altieri, Mar 04 '13 at 10:37
Also, (this is gonna sound really stupid bt i need to know) where exactly am I passing/storing the employeeId in the querystring?? — who-aditya-nawandar, Mar 04 '13 at 10:38
context.Request.QueryString("employeeId") is null actually (as in "") — who-aditya-nawandar, Mar 04 '13 at 10:42
In the Image1.ImageUrl = ... you are setting the employee id — Stefano Altieri, Mar 04 '13 at 10:42
Also you don't need to call ProcessRequest(Context) from the page. Probably this is the reason why you are getting the error — Stefano Altieri, Mar 04 '13 at 10:44
so how(& where) do i call it then? and where(& when) does this come into picture: — who-aditya-nawandar, Mar 04 '13 at 10:48
I really appreciate your help here but could you plz elaborate a little... If I am not wrong you are talking about the image control in html... I cant seem to get the syntax rt for the image url.. this is what i have: — who-aditya-nawandar, Mar 04 '13 at 11:00
the imageUrl attribute seems to be wrong. It should be: imageUrl="HttpHandler.ashx?EmployeeID=18" — Stefano Altieri, Mar 04 '13 at 11:02
I debugged the code and I think its got something to do with postback... I think the processrequest causes a postback... how can i avoid that? — who-aditya-nawandar, Mar 04 '13 at 11:51
You DON'T HAVE TO CALL the process request directly.. just via url... there is no postback. there is a get for the page and a get for each image you need. — Stefano Altieri, Mar 04 '13 at 11:57

score 0 · Answer 1 · answered Mar 04 '13 at 09:45

0

Generic Handler May helps you..

answered Mar 04 '13 at 09:45

Manoj Kumar Yellapragada

132
1
11

Ravinder Gujiri · Answer 2 · 2013-03-04T11:19:51.613

0

your handler should be like this

Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
Dim employeeId As Integer
If (Not (context.Request.QueryString("employeeId")) Is Nothing) Then
employeeId = Convert.ToInt32(context.Request.QueryString("employeeId"))
Dim con As SqlConnection("your connection string")    
Dim cmd As SqlCommand("select image_colum from <table_name> where employeeID = "+employeeID)
con.Open()
Dim dr As SqlDataReader = cmd.ExecuteReader()
dr.Read()
Dim picture As Byte() = dr[0]
context.Response.ContentType = "image/jpeg"
context.Response.BinaryWrite(picture)
End If
End Sub

edited Mar 04 '13 at 11:19

answered Mar 04 '13 at 10:19

Ravinder Gujiri

1,494
10
14

Error - "Response is not declared" – who-aditya-nawandar Mar 04 '13 at 10:32
check now! use context.Response – Ravinder Gujiri Mar 04 '13 at 10:54
"queryoutput is not declared" – who-aditya-nawandar Mar 04 '13 at 10:55
and whats the difference between my code and yours...? array name can be anything rt?? – who-aditya-nawandar Mar 04 '13 at 10:56
queryoutput means the result of your sql query – Ravinder Gujiri Mar 04 '13 at 11:10
so what do I write there?? where do I get the output of my query?? – who-aditya-nawandar Mar 04 '13 at 11:14

displaying image (from database) in an image control

2 Answers2

Linked