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Using Clipboard Class in ASP.NET

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Oleg Fridman asked on 31 Mar 2006, 06:44 PM

Using the clipboard class in C# or VB.NET is pretty simple for windows applications. However, it gets a little trickier for ASP.Net projects.

Background:
The first question you may ask is "Why would you ever want to use the server's clipboard to do anything?" Good question :). I came accross this problem when I was trying to write a pdf parser that would rasterize the front page and save it into a Bitmap object. From here, you can save it to a file, database, etc. To do this, I was using the Adobe Acrobat com library that comes with Adobe Acrobat 7.0. Unfortunatly, they do not have a function that allows you to simply save to a file. They do, however, let you copy the image to the clipboard and then recover it in whatever format you want.

Problem:
I found some great code here: http://www.codeproject.com/dotnet/pdfthumbnail.asp. This code was written for a C#/VB.Net Windows App and works great if used that way. However, when I tried to use this text in the OnClick event of an ASP Button control, i found that nothing was happening. Turns out, the CopyToClipboard command was working fine, b/c if I traced through, I could press ctrl+v and see the image perfectly. However, when the Clipboard.GetObject method was called, it was always returning Null.

Solution:
After much digging and 2 days of work, I stumbled on the reason: The thread started for the ASP.Net application did not have the right ApartmentState to read the Clipboard class. So, here is what I did to work around this:

protected void Button_Click(object sender, EventArgs e)
{
Thread cbThread = new Thread(new ThreadStart(CopyToClipboard));
cbThread.ApartmentState = ApartmentState.STA;
cbThread.Start();
cbThread.Join();
}

[STAThread]
protected void CopyToClipboard()
{
/*
In here, put the code that copies AND retrieves from the clipboard.
If you use global variables, the Bitmap you populate here can be used elsewhere in your code.
*/
}

Final Notes:
I do not recommend doing this in a multi-user environment as there is no guarentee that the user that copied to the clipboard will be the one who retrieves from it. Also, images/pdfs can be very large and the clipboard is slow.

I hope this is of some use to someone. It solved my problem and saved me $900 by not having to buy a PDF Rasterizer control. Feel free to respond and let me know if it helped you out or if you have any questions.

~ Oleg Fridman

Jamil

commented on 09 Feb 2022, 05:14 PM

Hello,

there are many ways to copy to clipboard:

Make sure to add the namespaces.

First Example:

using System;
using System.Windows;

public class Program
{
	public static void Main()
	{  
		Clipboard.SetText("Hello, clipboard");
		Console.WriteLine(input);
	}
}

Example 2

using System;
using System.Threading.ThreadStateException;

public class Program
{
	public static void Main()
	{  
		Thread thread = new Thread(() => Clipboard.SetText("String to be copied to clipboard"));
		thread.SetApartmentState(ApartmentState.STA); //Set the thread to STA
		thread.Start(); 
		thread.Join();
	}
}

Copy to Clipboard in C#

18 Answers, 1 is accepted

answered on 17 Oct 2006, 02:36 PM

Hey Sam,

Thanks for your interest in this code.

Try this for me:

Put a break in the code right before the "Clipboard.GetDataObject();" line but after the pdfPage.CopyToClipboard(pdfRect, 0, 0, 100); line.

Now, when the break hits, open up Paint on the server (or even Clipboard viewer), and see if there is anything there. If there is, what type is it? If you did it with paint, you should be able to hit Edit->Paste and see the pdf file in paint.

Also, are you sure you are running the line "Clipboard.Clear();"?

I have heard of problems with multiple items in the clipboard if it is not cleared every time.

I was not able to find much online about this error...

Sorry Sam. Give those two things a shot and let me know.

-Oleg Fridman

answered on 26 Oct 2006, 03:47 AM

Hi,

We are actually using the adobe acrobat 6.0 sdk for generating the thumbnails of the pdf pages. using the code from the following link.

And this code is working fine on the win200o professional and Xp professional OS which is running with IIS5.0.

When we run this code on win2003 server machine which is running with IIS6.0 by default this code is not running properly. The main problem is we find out is with the introduction of new application pool concept in IIS6.0.

If we change the worker process isolation mode in IIS6.0 to be compatible with IIS 5.0 then the code runs fine but the report server(SQL server reporting services 2005) installed on the machine stops working.

We are not able to find the solution for this.

Note: To change the isolation mode in IIS 6.0. Here the link to find the step for this one

http://technet2.microsoft.com/WindowsServer/en/library/d8bb3775-2731-4846-8c26-1c958a58fc281033.mspx?mfr=true

answered on 15 Feb 2007, 10:16 PM

Oleg,
hi! code is working in win xp and .net framework 2005, but i have problems with .net 2003, this don't work.
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim cbThread As Threading.Thread

cbThread = New Threading.Thread(New Threading.ThreadStart(AddressOf CopyToClipboard))

cbThread.ApartmentState = Threading.ApartmentState.STA

cbThread.Start()

cbThread.Join()

End Sub

<STAThread()> _

Protected Sub CopyToClipboard()

Dim objClipboard As IDataObject

objClipboard = Clipboard.GetDataObject

If Not objClipboard Is Nothing Then

If (objClipboard.GetDataPresent(DataFormats.Bitmap)) Then

' never enter here

Dim pBitmap As Bitmap

pBitmap = objClipboard.GetData(DataFormats.Bitmap)

pBitmap.Save("C:\Inetpub\wwwroot\images\imgtemp.bmp")

Me.Image1.ImageUrl = "http:\\localhost\images\imgtemp.bmp"

End If

End Sub

if you help mee i apprecired.

Cu

answered on 19 Oct 2010, 11:46 PM

Hi samir,

You can use HttpContext.Current.Response.AddHeader and HttpContext.Current.Response.ContentType methods inside a custom HttpHandler.

To open the file as an attachment you can use

response.AddHeader("content-disposition", "attachment; filename=" + contentSettings.FileName);

To open the file inline you can use

response.AddHeader("content-disposition", "inline; filename=" + contentSettings.FileName);

You could also open the document inside another custom control as shown in this demo or iframe.

Best wishes,
Ivan Dimitrov
the telerik team

www.telerik.com | dnn.telerik.com | www.sharepointcontrols.com | www.sitefinity.com | www.mcmscontrols.com