Display dot-dot-dot progress in a WPF button

The simplest way of doing that is using an ObjectAnimationUsingKeyFrames. Set the TargetProperty on the Content and set the Value of each DiscreteObjectKeyFrame to Reconciling. Reconciling.. Reconciling....

Example for a ControlTemplate with a ContentPresenter named PART_Content:

<ControlTemplate.Triggers>    <Trigger Property="IsEnabled" Value="False">        <Trigger.EnterActions>            <BeginStoryboard>                <Storyboard>                    <ObjectAnimationUsingKeyFrames Storyboard.TargetName="PART_Content" Storyboard.TargetProperty="Content" Duration="00:00:00.8" RepeatBehavior="Forever">                        <DiscreteObjectKeyFrame KeyTime="00:00:00.0" Value="Loading"/>                        <DiscreteObjectKeyFrame KeyTime="00:00:00.2" Value="Loading."/>                        <DiscreteObjectKeyFrame KeyTime="00:00:00.4" Value="Loading.."/>                        <DiscreteObjectKeyFrame KeyTime="00:00:00.6" Value="Loading..."/>                    </ObjectAnimationUsingKeyFrames>                </Storyboard>            </BeginStoryboard>        </Trigger.EnterActions>    </Trigger></ControlTemplate.Triggers>