WPF/C# Don't block the UI

Question

I\'ve an existing WPF application, which has several sections. Every section is a UserControl, that implements an interface.

The interface specify two methods:

Answer 1

Treat UnloadData as a async operation and let the async/await features handle both the case when it completes synchronously and when it needs to complete asynchronously:

public async Task UnloadData(){
    if(...){
        // The await keyword will segment your method execution and post the continuation in the UI thread
        // The Task.Factory.StartNew will run the time consuming method in the ThreadPool
        await Task.Factory.StartNew(()=>LaunchMyTimeConsumingMethodWithBackgroundWorker());
        // The return statement is the continuation and will run in the UI thread after the consuming method is executed
        return true;
    }
    // If it came down this path, the execution is synchronous and is completely run in the UI thread       
    return false;
}


private async void button_Click(object sender, RoutedEventArgs e)
{
        // Put here your logic to prevent user interaction during the operation's execution.
        // Ex: this.mainPanel.IsEnabled = false;
        // Or: this.modalPanel.Visibility = Visible;
        // etc

        try
        {
            bool result = await this.UnloadData();
            // Do whatever with the result
        }
        finally
        {
            // Reenable the user interaction
            // Ex: this.mainPanel.IsEnabled = true;
        }
}

EDIT

If you can't modify the UnloadData, then just execute it on the ThreadPool, as @BTownTKD noted:

    private async void button_Click(object sender, RoutedEventArgs e)
{
        // Put here your logic to prevent user interaction during the operation's execution.
        // Ex: this.mainPanel.IsEnabled = false;
        // Or: this.modalPanel.Visibility = Visible;
        // etc

        try
        {

            // The await keyword will segment your method execution and post the continuation in the UI thread
            // The Task.Factory.StartNew will run the time consuming method in the ThreadPool, whether it takes the long or the short path
            bool result = await The Task.Factory.StartNew(()=>this.UnloadData());
            // Do whatever with the result
        }
        finally
        {
            // Reenable the user interaction
            // Ex: this.mainPanel.IsEnabled = true;
        }
}