Clipboard backup in C#

• Download demo project - 14.4 Kb
• Download source - 22.4 Kb

Introduction

The code uses Windows API calls to read and write into the clipboard.

It provides a ClipboardHelper, an easy to use API bridge, which offers, in addition, functions to serialize complex clipboard data to hard disk and restore them when you want, using the XmlSerializer, instead of the .NET Framework which can manage only CLR compliant data.

I tested it with Internet Explorer, Word, OpenOffice, including with image files.

Background

The .NET framework and the Windows.Forms.Clipboard class allows to manipulate only serializable data. So what happens if your clipboard contains data from a non-compliant application? Easy! The .NET Framework thinks that the clipboard is empty.

To read and manipulate these data, we need to call user32.dll and kernerl32.dll.

Using the code

The code includes two projects: the library ClipboardHelper, and the console application ClipboardTest.

The whole code is commented, to understand the API usage and the implemented saving process.

To use the library is really easy: it's a static class that exposes a static void ClipboardHelper.Serialize function to serialize the clipboard data to hard disk, and static void Deserialize to deserialize it and place it back into the clipboard, ready to be pasted.

//Comment next line to end the demo mode
//and backup your clipboard data.
ClipboardHelper.Deserialize(demo);
Console.WriteLine("restore the demo clipboard");

//Open the clipboard and serialize into a directory
ClipboardHelper.Serialize(fileName);
Console.WriteLine("serialize clipboard to " + fileName);

//Deserialize the clipboard and set data
//to win clipboard ready to be pasted
ClipboardHelper.Deserialize(fileName);
Console.WriteLine("restore the clipboard " + fileName);

The test application shows an example of the ClipboardHelper in action. It deserializes the clipboard, after having copied some rows from Internet Explorer at the CodeProject homepage, backs it up, and deserializes it again, from the backup. After you run it, you have the clipboard backup in your own clipboard, ready to be pasted.

Inside the ClipboardHelper

Data returned by API calls are saved in [Serializable]DataClip objects. It allows to easily send the clipboard in a remoting context, and to save it via the XmlSerializer:

public static void SaveToFile(ReadOnlyCollection<DATACLIP> clipData, string clipName)
{
    IEnumerator<DATACLIP> cData = clipData.GetEnumerator();
    while (cData.MoveNext())
    {
        XmlSerializer xml = new XmlSerializer(typeof(DataClip));
        using (StreamWriter sw = new StreamWriter(di.FullName + 
                                 @"\" + i.ToString() + ".cli",false))
        {
            xml.Serialize(sw, cData.Current);
        }
    }
 }

Deep into the clipboard

The clipboard contains data in fragmented buffers. Each of them has a specific DataFormat that is used by the clipboard viewer and the software from which data has been copied, to recognize how to correctly render the buffer.

The function EnumClipboardFormats of user32.dll returns the array of DataFormats contained in the clipboard. For each DataFormat, we can call GetClipboardData. It returns the handle to the clipboard object. By calling GlobalSize and GlobalLock from kernel32.dll, we obtain the clipboard object properties (its length and the pointer to it), so we can copy the clipboard object into our buffer (a byte array) via the Marshal.Copy method.

To get the clipboard, first of all, check to open the clipboard:

Win32ClipboardAPI.OpenClipboard(IntPtr.Zero)

Then, we get all DataFormats; querying them we get the clipboard data buffer:

    //Init a list of ClipData,
    // which will contain each Clipboard Data
    List<DataClip> clipData = new List<DataClip>();
    //Loop for each clipboard data type
    uint format = 0;
    while ((format = Win32ClipboardAPI.EnumClipboardFormats(format)) != 0)
    {
        //Get the formatName
        StringBuilder formatName = new StringBuilder();
        Win32ClipboardAPI.GetClipboardFormatName(format, 
                                       formatName, 100);
        
        //Get the pointer for the current Clipboard Data 
        IntPtr pos = Win32ClipboardAPI.GetClipboardData(format);
        //Get the clipboard buffer data properties
        UIntPtr lenght = Win32MemoryAPI.GlobalSize(pos);
        IntPtr gLock = Win32MemoryAPI.GlobalLock(pos);
        byte[] buffer;
        //Init a buffer which will contain the clipboard data
        buffer = new byte[(int)lenght];
        int l = Convert.ToInt32(lenght.ToString());
        //Copy data from clipboard to our byte[] buffer
        Marshal.Copy(gLock, buffer, 0, l);
        //Create a ClipData object that 
        //represents the current clipboard data
        DataClip cd = new DataClip(format, 
                      formatName.ToString(), buffer);
        //Add current Clipboard Data to the list
        clipData.Add(cd);
}

History

• 08/23/2006 - Initial release.
• 08/29/2006 - The whole saving system has been changed, implementing the XmlSerializer. It works better, solving the bugs in the writing file process.