Help with Linq Expression - INotifyPropertyChanged
- by Stephen Patten
Hello,
I'm reading the source code from the latest Prism 4 drop and am interested in solving this problem. There is a base class for the ViewModels that implements INotifyPropertyChanged and INotifyDataErrorInfo and provides some refactoring friendly change notification.
protected void RaisePropertyChanged<T>(Expression<Func<T>> propertyExpresssion)
{
var propertyName = ExtractPropertyName(propertyExpresssion);
this.RaisePropertyChanged(propertyName);
}
private string ExtractPropertyName<T>(Expression<Func<T>> propertyExpresssion)
{
if (propertyExpresssion == null)
{
throw new ArgumentNullException("propertyExpression");
}
var memberExpression = propertyExpresssion.Body as MemberExpression;
if (memberExpression == null)
{
throw new ArgumentException("The expression is not a member access expression.", "propertyExpression");
}
var property = memberExpression.Member as PropertyInfo;
if (property == null)
{
throw new ArgumentException("The member access expression does not access property.","propertyExpression");
}
if (!property.DeclaringType.IsAssignableFrom(this.GetType()))
{
throw new ArgumentException("The referenced property belongs to a different type.", "propertyExpression");
}
var getMethod = property.GetGetMethod(true);
if (getMethod == null)
{
// this shouldn't happen - the expression would reject the property before reaching this far
throw new ArgumentException("The referenced property does not have a get method.", "propertyExpression");
}
if (getMethod.IsStatic)
{
throw new ArgumentException("The referenced property is a static property.", "propertyExpression");
}
return memberExpression.Member.Name;
}
and as an example of it's usage
private void RetrieveNewQuestionnaire()
{
this.Questions.Clear();
var template = this.questionnaireService.GetQuestionnaireTemplate();
this.questionnaire = new Questionnaire(template);
foreach (var question in this.questionnaire.Questions)
{
this.Questions.Add(this.CreateQuestionViewModel(question));
}
this.RaisePropertyChanged(() => this.Name);
this.RaisePropertyChanged(() => this.UnansweredQuestions);
this.RaisePropertyChanged(() => this.TotalQuestions);
this.RaisePropertyChanged(() => this.CanSubmit);
}
My question is this. What would it take to pass an array of the property names to an overloaded method (RaisePropertyChanged) and condense this last bit of code from 4 lines to 1?
Thank you,
Stephen
