Retrieving text data from clipboard

Clipboard class has a method, GetDataObject() which retrieves the data that is currently in the system clipboard. In fact GetDataObject() returns an object that implements the IDataObject interface, which has 3 dominant methods(GetDataPresent, GetData and GetFormats).

GetDataPresent - Determines if the current data in Clipboard can be converted to the format we specify.

GetData - Retrieves the data associated with the format we specify from Windows Clipboard.

Note: DataFormats class has predefined Clipboard data format names, which can be provided to the above 2 methods as parameter to verify the data format.

Listing 1 – Retrieve text data from Clipboard

if (Clipboard.GetDataObject().GetDataPresent(DataFormats.Text))
{
  string s = Clipboard.GetDataObject().GetData(DataFormats.Text).ToString();
}

In the above piece of code, GetData method is used to retrieve data from the system Clipboard. The format of the data to be retrieved is provided as parameter. As the system Clipboard is shared by multiple applications, before retrieving data, we must ensure that the format of current clipboard data is the same that our application expects. So we make a check for the data format of the data to be retrieved, with a call to GetDataPresent method. GetDataPresent method returns a boolean value which determines whether the current data on the Clipboard can be converted to the data format we specify. To specify the data format, it is advisable to use the DataFormats class which contains static fields representing system Clipboard formats. DataFormats.Text is provided for string data. Alternative to using the DataFormats class is to provide the name of the format as string.

Setting text data to Clipboard

Clipboard class has a method, SetDataObject(). This method places the specified data on the Clipboard. This method has 3 interesting overloaded clones.

SetDataObject(object data) - Places data on the system Clipboard.
Note: The data placed on Clipboard by this method is non-persistent, ie., the data is not retained on Clipboard once the application exits. 

SetDataObject(object data, bool copy) - Places data on the system Clipboard and specifies whether the data should remain on the Clipboard after the application exits. 

SetDataObject(object data, bool copy, int RetryTimes, int RetryDelay) - Attempts to place data on the system Clipboard the specified number of times and with the specified delay between attempts.

Listing 2 – Setting text data to Clipboard

Clipboard.SetDataObject("C# is the best", true);

In the above piece of code, SetDataObject method sets string "C# is the best" on the System Clipboard. The text remains on the clipboard till it is replaced by any application. And the string remains there even after our application exits, because the second parameter of the method is set to true, which indicates the data to be persistent.

Retrieving image from Clipboard

This is exactly the same as retrieving text data, except that the data format given is DataFormats.Bitmap instead of DataFormats.Text

Listing 3 – Retrieving image from Clipboard

if (Clipboard.GetDataObject().GetDataPresent(DataFormats.Bitmap))
{
  Bitmap bmp = (Bitmap)Clipboard.GetData(DataFormats.Bitmap);
}

GetDataPresent method verifies if an image (bitmap) object is present on clipboard and GetData method retrieves the image as a bitmap object.

An alternative for this in .NET 2.0 is

Listing 4 - Retrieving image from Clipboard(Alternative)

if (Clipboard.GetDataObject().GetDataPresent(DataFormats.Bitmap))
{
  Bitmap bmp = (Bitmap)Clipboard.GetImage();
}

The GetImage method returns an Image object which can be directly assigned to Image objects or controls.

Setting Image to Clipboard

This is also similar to setting text to clipboard.

Listing 5 - Setting Image to Clipboard

Clipboard.SetDataObject((Bitmap)lstBoxCpyItms.SelectedItem, true);

The overloaded versions of SetDataObject has been explained earlier, in this article.

Till now our discussion has been about the basic usage of the Clipboard class.

Now we shall get into the ClipboardRing application.