How to cancel asynchronous document loading in SfRichTextBoxAdv control?

//Represents the document loading task.
Task<bool> loadAsync = null;
//Represents the cancellation token source.
CancellationTokenSource cancellationTokenSource = null;

if (stgFile != null)
{
bool showErrorMsg = false;
string errormessage = string.Empty; 
    try 
    { 
        //Instantiates new cancellation token source.
        cancellationTokenSource = new CancellationTokenSource(); 
        //Invokes the asynchronous load method of SfRichTextBoxAdv.
        loadAsync = this.richTextBox.LoadAsync(stgFile, cancellationTokenSource.Token); 
        await loadAsync; 
    } 
    catch(Exception ex) 
    { 
        showErrorMsg = true; 
        errormessage = ex.Message; 
    } 
    if (showErrorMsg) 
    { 
        //Handles the error faced while loading the document in SfRichTextBoxAdv.
        if (!cancellationTokenSource.IsCancellationRequested) 
        { 
            MessageDialog dialog = null; 
            if (errormessage.Contains("Access is denied")) 
                dialog = new MessageDialog("This file cannot be open because it is being used by another process"); 
            else 
                dialog = new MessageDialog("The input document could not be processed completely, Could you please email the document to support@syncfusion.com for troubleshooting."); 
            await dialog.ShowAsync(); 
        } 
    } 
} 
//Disposes the cancellation token source
if (cancellationTokenSource != null) 
    cancellationTokenSource.Dispose(); 
cancellationTokenSource = null; 
loadAsync = null; 
 
 

 
async void DocumentEditor_Unloaded(object sender, RoutedEventArgs e) 
{ 
    //Checks if the document load task is executing asynchronously. 
    if (loadAsync != null && !loadAsync.IsCompleted && !loadAsync.IsFaulted && cancellationTokenSource != null) 
    { 
        //Invokes the cancel method, to cancel the asynchronous load operation
        cancellationTokenSource.Cancel(); 
        try 
        { 
            //Holds the execution for cancel operation to be completed.
            await loadAsync; 
        } 
        catch 
        { } 
    } 
    //Unhooks the events of SfRichTextBoxAdv.
    this.richTextBox.RequestNavigate -= RichTextBoxAdv_RequestNavigate; 
    this.richTextBox.SelectionChanged -= RichTextBox_SelectionChanged; 
    this.richTextBox.ContentChanged -= RichTextBox_ContentChanged; 
    //Disposes the resources used by SfRichTextBoxAdv explicitly. 
    this.richTextBox.Dispose(); 
    this.richTextBox = null; 
}