/// <summary>
/// Adds a weak event handler info.
/// </summary>
/// <param name="weakHandlerInfos">The target weak event handler info collection.</param>
/// <param name="target">The target instance if the event handler is a instance method; otherwise null.</param>
/// <param name="methodInfo">The event handler method info.</param>
/// <returns>A new weak event handler info collection.</returns>
public static IEnumerable <WeakEventHandlerInfo> Add(this IEnumerable <WeakEventHandlerInfo> weakHandlerInfos, object target, MethodInfo methodInfo)
{
if (weakHandlerInfos == null)
{
throw new ArgumentNullException(nameof(weakHandlerInfos));
}
if (methodInfo == null)
{
throw new ArgumentNullException(nameof(methodInfo));
}
var newWeakHandlerInfos = new WeakEventHandlerInfo[weakHandlerInfos.Count() + 1];
// Copies existing event handler infos.
int index = 0;
foreach (var weakHandlerInfo in weakHandlerInfos)
{
newWeakHandlerInfos[index++] = weakHandlerInfo;
}
// Copies the new event handler info.
newWeakHandlerInfos[index] = new WeakEventHandlerInfo(target, methodInfo);
// Returns the weak event handler info collection.
return(newWeakHandlerInfos);
}
/// <summary>
/// Removes a weak event handler info.
/// </summary>
/// <param name="weakHandlerInfos">The target weak event handler info collection.</param>
/// <param name="target">The target instance if the event handler is a instance method; otherwise null.</param>
/// <param name="methodInfo">The event handler method info.</param>
/// <returns>A new weak event handler info collection if the event handler info is removed; otherwise the target weak event handler info collection.</returns>
public static IEnumerable <WeakEventHandlerInfo> Remove(this IEnumerable <WeakEventHandlerInfo> weakHandlerInfos, object target, MethodInfo methodInfo)
{
if (weakHandlerInfos == null)
{
throw new ArgumentNullException(nameof(weakHandlerInfos));
}
if (methodInfo == null)
{
throw new ArgumentNullException(nameof(methodInfo));
}
// Finds the weak event handler info to delete.
var weakHandlerInfoToDelete = weakHandlerInfos.FirstOrDefault
(
weakHandlerInfo =>
{
return(weakHandlerInfo.WeakTarget.Target == target &&
weakHandlerInfo.MethodInfo == methodInfo);
}
);
// If there is no weak event handler info to delete...
if (weakHandlerInfoToDelete == null)
{
return(weakHandlerInfos);
}
var newWeakHandlerInfos = new WeakEventHandlerInfo[weakHandlerInfos.Count() - 1];
int index = 0;
foreach (var weakHandlerInfo in weakHandlerInfos)
{
// Skips the weak event handler info to delete.
if (weakHandlerInfo == weakHandlerInfoToDelete)
{
continue;
}
newWeakHandlerInfos[index++] = weakHandlerInfo;
}
// Returns the weak event handler info collection.
return(newWeakHandlerInfos);
}
/// <summary>
/// Cleans up event handlers that the target objects are garbage collected.
/// </summary>
/// <param name="weakHandlerInfos">The target weak event handler info collection.</param>
/// <param name="sender">The event sender.</param>
/// <param name="args">The event arguments.</param>
/// <param name="invokeHandler">If this parameter is true, alive event handlers are invoked.</param>
/// <returns>A new weak event handler info collection if garbage collected event handler infos are removed; otherwise the target weak event handler info collection.</returns>
public static IEnumerable <WeakEventHandlerInfo> Cleanup(this IEnumerable <WeakEventHandlerInfo> weakHandlerInfos, object sender, object args, bool invokeHandler)
{
if (weakHandlerInfos == null)
{
throw new ArgumentNullException(nameof(weakHandlerInfos));
}
List <WeakEventHandlerInfo> weakHandlerInfosToDelete = null;
// For each weak handler info...
foreach (var weakHandlerInfo in weakHandlerInfos)
{
// If the event handler is a static method...
if (weakHandlerInfo.MethodInfo.IsStatic)
{
// Calls the event handler.
if (invokeHandler)
{
weakHandlerInfo.MethodInfo.Invoke(null, new object[] { sender, args });
}
}
else
{
// Gets the strong reference.
object target = weakHandlerInfo.WeakTarget.Target;
// If it is garbage collected..
if (target == null)
{
if (weakHandlerInfosToDelete == null)
{
weakHandlerInfosToDelete = new List <WeakEventHandlerInfo>();
}
// Collects the garbage collected event handler info.
weakHandlerInfosToDelete.Add(weakHandlerInfo);
continue;
}
// Calls the event handler.
if (invokeHandler)
{
weakHandlerInfo.MethodInfo.Invoke(target, new object[] { sender, args });
}
}
}
// If no event handler info is garbage collected..
if (weakHandlerInfosToDelete == null)
{
return(weakHandlerInfos);
}
// If all event handlers are garbage collected..
int weakHandlerInfoCount = weakHandlerInfos.Count();
if (weakHandlerInfosToDelete.Count == weakHandlerInfoCount)
{
return(Enumerable.Empty <WeakEventHandlerInfo>());
}
var newWeakHandlerInfos = new WeakEventHandlerInfo[weakHandlerInfoCount - weakHandlerInfosToDelete.Count];
int index = 0;
foreach (var weakHandlerInfo in weakHandlerInfos)
{
// Skips the event handler info garbage collected
if (weakHandlerInfosToDelete.Contains(weakHandlerInfo))
{
continue;
}
newWeakHandlerInfos[index++] = weakHandlerInfo;
}
// Returns the weak event handler info collection.
return(newWeakHandlerInfos);
}