/// <summary>
/// Tries to get a class instance for a given attribute type. All loaded assemblies are searched for classes that attributeType applies to,
/// then for all found classes the instantiation of a class is tried, until a instance is created successfully. Here, the attributeType has
/// to implement <see cref="IClassForClassAttribute" />, and creationArg[0] has to match the type in <see cref="IClassForClassAttribute.TargetType" />
/// </summary>
/// <param name="attributeType">The type of attribute the class(es) to instantiate must be assigned to.</param>
/// <param name="expectedTypes">The expected type of return value.</param>
/// <param name="creationArgs">The creation arguments used to instantiate a class.</param>
/// <param name="overrideArgs0Type">Usually null. If you provide a type here, it has to be a base type of the typeof(creationArgs[0]). By this you
/// can "downgrade" creationArgs[0], so that only attributes for the base type are looked for.</param>
/// <returns>The instance of the first class for which the instantiation was successfull and results in the expectedType. Otherwise null.</returns>
/// <remarks>The instantiation is tried first with the full argument list. If that fails, the last element of the argument list is chopped and the instantiation is tried again.
/// This process is repeated until the instantiation was successfull or the argument list is empty (empty constructor is tried at last).</remarks>
public static object GetClassForClassInstanceByAttribute(System.Type attributeType, System.Type[] expectedTypes, object[] creationArgs, System.Type overrideArgs0Type)
{
// 1st search for all classes that wear the UserControllerForObject attribute
IAttributeForClassList list = ReflectionService.GetAttributeInstancesAndClassTypesForClass(attributeType, creationArgs[0], overrideArgs0Type);
return(CreateInstanceFromList(list, expectedTypes, creationArgs));
}
/// <summary>
/// Tries to get a class instance for a given attribute type. All loaded assemblies are searched for classes that attributeType applies to,
/// then for all found classes the instantiation of a class is tried, until a instance is created successfully. Here, the attributeType has
/// to implement <see cref="IClassForClassAttribute" />, and creationArg[0] has to match the type in <see cref="IClassForClassAttribute.TargetType" />
/// </summary>
/// <param name="list">The list of types to try for creation.</param>
/// <param name="expectedTypes">The expected types of return value.</param>
/// <param name="creationArgs">The creation arguments used to instantiate a class.</param>
/// <returns>The instance of the first class for which the instantiation was successfull and results in the expectedType. Otherwise null.</returns>
/// <remarks>The instantiation is tried first with the full argument list. If that fails, the last element of the argument list is chopped and the instantiation is tried again.
/// This process is repeated until the instantiation was successfull or the argument list is empty (empty constructor is tried at last).</remarks>
public static object CreateInstanceFromList(IAttributeForClassList list, System.Type[] expectedTypes, object[] creationArgs)
{
object result = null;
// evaluate the len of the creation args without null's as arguments
int trueArgLen = creationArgs.Length;
for (int i = 0; i < creationArgs.Length; i++)
{
if (creationArgs[i] == null)
{
trueArgLen = i;
break;
}
}
System.Type[][] creationTypes = new Type[trueArgLen + 1][];
foreach (Type definedType in list.Types)
{
if (!IsSubClassOfOrImplements(definedType, expectedTypes))
{
continue;
}
// try to create the class
for (int j = trueArgLen; j >= 0; j--)
{
if (creationTypes[j] == null)
{
creationTypes[j] = new Type[j];
for (int k = j - 1; k >= 0; k--)
{
creationTypes[j][k] = creationArgs[k].GetType();
}
}
ConstructorInfo cinfo = definedType.GetConstructor(creationTypes[j]);
if (cinfo != null)
{
object[] chopped = null;
if (j < creationArgs.Length)
{
chopped = new object[j];
Array.Copy(creationArgs, chopped, j);
}
result = cinfo.Invoke(j == creationArgs.Length ? creationArgs : chopped);
if (result != null)
{
return(result);
}
}
}
}
return(result);
}
