Hi,
Within a Single Button Event If you want to Execute More than one condition what you can do is
According to your Example what you can do is, within the Button event check the text of the Button and Give the Operations Accordingly.
Eg:-
protected void BtnPlay_Click(object sender, ImageClickEventArgs e)
{
if(BtnPlay.Text=="Play")
{
BtnPlay.Text="Pause";
} else if(BtnPlay.Text=="Pause")
{
BtnPlay.Text="Play";
}
}