Posted by: denniszeng2008 on: March 26, 2009
Here are something that i learned from sample projects.(Blogengine.Net)
1.You should make full use of Object Oriented Concept.
a.Provider Model.
When you design a core engine for blog, you should first design the core module.
It will contain abstract class and interfaces which will help you to extend and manage the functions later.
ProviderBase(it is a buildin class, that offer the function to commnicate with settings with web.config. that’s the benefit of extend
|| /*because of the extend, you can fully utilize ProviderBase class. Use XML file the dynamic set the database provider without change your code. After you add new functions
|| to BlogProvider, it will offer a model for later extend. for example: XMLProvider and DbBlogProvider, they are all ProviderBase object ! They have the same functions from
\/ ProviderBase. */
BlogProvider
|| /* And when later use of these class(XMLProvider and DbBlogProvider) will be consider as BlogProvider; BlogProvider dbBlogProvider= new DbBlogProvider();
|| This is a abstract process, It seems like there are a layer between DbBlogProvider and Database, when you change your database provider you didn’t need to change
\/ The code.*/
(XMLProvider or DbBlogProvider)
||
||
\/
BlogService (use the data and functions provided by BlogProvider at the upper layer to offer the capability of retrieve and update data from database. As well as the basic logical.)
private static void LoadProviders()
{
// Avoid claiming lock if providers are already loaded
if (_provider == null)
{
lock (_lock)
{
// Do this again to make sure _provider is still null
if (_provider == null)
{
// Get a reference to the <blogProvider> section
BlogProviderSection section = (BlogProviderSection)WebConfigurationManager.GetSection(“BlogEngine/blogProvider”);
// Load registered providers and point _provider
// to the default provider
_providers = new BlogProviderCollection();
ProvidersHelper.InstantiateProviders(section.Providers, _providers, typeof(BlogProvider));
_provider = _providers[section.DefaultProvider];
if (_provider == null)
throw new ProviderException(“Unable to load default BlogProvider”);
}
}
}
}
…………………………………Use these code to set different Provider for this BlogService(Offer basic function for operate on database)…………………………………
So from this , when you start a new project, you should think about how to utilize system buildin class and make use of them. Like language Localization and IHttpModule and so on.
b.Interface
public abstract class BusinessBase<TYPE, KEY> : IDataErrorInfo, INotifyPropertyChanged, IChangeTracking, IDisposable where TYPE : BusinessBase<TYPE, KEY>, new()
protected virtual void MarkChanged(string propertyName)
{
_IsChanged = true;
if (!_ChangedProperties.Contains(propertyName))
{
_ChangedProperties.Add(propertyName);
}
OnPropertyChanged(propertyName);
}
public event PropertyChangedEventHandler PropertyChanged;
/// <summary>
/// Raises the PropertyChanged event safely.
/// </summary>
protected virtual void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
They are all in the BusinessBase class, Do you see anything ?
BusinessBase class extend the INotifyPropertyChanged interface:
// Summary:
// Notifies clients that a property value has changed.
public interface INotifyPropertyChanged
{
// Summary:
// Occurs when a property value changes.
event PropertyChangedEventHandler PropertyChanged;
}
It just contain a field of EventHandler, and the client can set the EventHandler function to call When property are modified outside. MarkChanged function will call OnPropertyChanged to indirect call the eventHandler set by client. And BusinessBase class implement this function for the descendants. When some field in BusinessBase changed it will call MarkChanged to indirect implement the eventHandler. That sounds very good, right ?
So this method is used to offer common method for descendants, very good!
<2> Leave the space for later reinforce
protected abstract void ValidationRules();//the descendant can implement this function and can be used by class outside.
/// <summary>
/// Gets whether the object is valid or not.
/// </summary>
public bool IsValid
{
get
{
ValidationRules();
return this._BrokenRules.Count == 0;
}
}
<3> use enum
virtual public SaveAction Save()
{
if (IsDeleted && !IsAuthenticated)
throw new System.Security.SecurityException(“You are not authorized to delete the object”);
if (!IsValid && !IsDeleted)
throw new InvalidOperationException(ValidationMessage);
if (IsDisposed && !IsDeleted)
throw new InvalidOperationException(string.Format(CultureInfo.InvariantCulture, “You cannot save a disposed {0}”, this.GetType().Name));
if (IsChanged)
{
return Update();
}
return SaveAction.None;
}
<4> use bitwise operation to implement privileges!!
<5>for extend
#region Data access
/// <summary>
/// Retrieves the object from the data store and populates it.
/// </summary>
/// <param name=”id”>The unique identifier of the object.</param>
/// <returns>True if the object exists and is being populated successfully</returns>
protected abstract TYPE DataSelect(KEY id);
/// <summary>
/// Updates the object in its data store.
/// </summary>
protected abstract void DataUpdate();
/// <summary>
/// Inserts a new object to the data store.
/// </summary>
protected abstract void DataInsert();
/// <summary>
/// Deletes the object from the data store.
/// </summary>
protected abstract void DataDelete();
#endregion
