Read original post by Scott Lovegrove at Windows Phone 7 Nuggets
Those doing development for Windows Phone or Windows 8 and using an MVVM approach will be familiar with their ViewModels having properties that look something like this
private
string
progressText;
public
string
ProgressText
{
get
{
return
progressText; }
set
{
if
(value != progressText)
{
progressText = value;
NotifyPropertyChanged(
"ProgressText"
);
}
}
}