/// <summary>
/// Creates a proxy for this object
/// </summary>
/// <typeparam name="I">Interface to proxy</typeparam>
/// <typeparam name="A">Will only proxy method that have this attribute</typeparam>
/// <param name="objectToProxy"></param>
/// <param name="interceptorDelegate">delegate to call on method invocation</param>
/// <returns></returns>
public static I Proxy <I, A>(this I objectToProxy, EmitProxyInterceptor <I> interceptorDelegate) where A : Attribute
{
return(Proxy <I>(objectToProxy, (info) =>
{
//Check if hte attribute is on the interface
//also check if our method info is actually a property value, if so we will check if the
//attribute is on the property
bool isAttributeOnInterface = typeof(I).GetMethod(info.Name, info.GetParameters().Select(p => p.ParameterType).ToArray()) != null;
if (isAttributeOnInterface == false && info.IsSpecialName && (info.Name.StartsWith("get_") || info.Name.StartsWith("set_")))
{
isAttributeOnInterface = typeof(I).GetProperty(info.Name.Remove(0, 4)) != null;
}
//Check if hte attribute is on our actual object
//also check if our method info is actually a property value, if so we will check if the
//attribute is on the property
bool isAttributeOnMethod = info.GetCustomAttributes(typeof(A), true).Count() > 0;
if (isAttributeOnMethod == false && info.IsSpecialName && (info.Name.StartsWith("get_") || info.Name.StartsWith("set_")))
{
isAttributeOnMethod = objectToProxy.GetType().GetProperty(info.Name.Remove(0, 4)) != null;
}
//we have the attribute if it is either on the interface or method
return isAttributeOnInterface || isAttributeOnMethod;
}, interceptorDelegate));
}
/// <summary>
/// Creates a proxy for this object
/// </summary>
/// <typeparam name="I">Interface to proxy</typeparam>
/// <param name="objectToProxy"></param>
/// <param name="interceptorDelegate">delegate to call on method invocation</param>
/// <returns></returns>
public static I Proxy <I>(this I objectToProxy, EmitProxyInterceptor <I> interceptorDelegate)
{
return(Proxy <I>(objectToProxy, (info) => true, interceptorDelegate));
}
/// <summary>
/// Creates a proxy for this object
/// </summary>
/// <typeparam name="I">Interface to proxy</typeparam>
/// <param name="objectToProxy"></param>
/// <param name="methodSelector">predicate to select which methods call the <paramref name="interceptorDelegate"/> </param>
/// <param name="interceptorDelegate">delegate to call on method invocation</param>
/// <returns></returns>
public static I Proxy <I>(this I objectToProxy, Predicate <MethodInfo> methodSelector, EmitProxyInterceptor <I> interceptorDelegate)
{
if (!typeof(I).IsInterface)
{
throw new Exception("Generic parameter must be an interface");
}
//ensure we have something in our interface level cache
if (!_dynamicTypeCache.ContainsKey(typeof(I)))
{
_dynamicTypeCache[typeof(I)] = new Dictionary <Predicate <MethodInfo>, Type>();
}
//Check if the type is cached first, if not we go and emit a proxy class for the given interface
//and pass null for the attribute we are proxying
if (!_dynamicTypeCache[typeof(I)].ContainsKey(methodSelector))
{
_dynamicTypeCache[typeof(I)][methodSelector] = CreateProxy <I>(objectToProxy, methodSelector, interceptorDelegate);
}
return((I)Activator.CreateInstance(_dynamicTypeCache[typeof(I)][methodSelector], objectToProxy, interceptorDelegate));
}
/// <summary>
/// Creates a proxy
/// </summary>
/// <typeparam name="I">Interface of the proxy</typeparam>
/// <param name="objectToProxy">object that is being proxied</param>
/// <param name="interceptorDelegate">delegate to call on invocation</param>
/// <param name="methodSelector">predicate to select which methods call the <paramref name="interceptorDelegate"/> </param>
/// <returns>The proxy</returns>
private static Type CreateProxy <I>(I objectToProxy, Predicate <MethodInfo> methodSelector, EmitProxyInterceptor <I> interceptorDelegate)
{
//create the dynamic assembly
ModuleBuilder moduleBuilder = CreateAssembly(ASSEMBLY_NAME, MODULE_NAME);
//create our new type that implements the proxy interface
TypeBuilder typeBuilder = moduleBuilder.CreateType <I, object>(typeof(I).Name + TYPE_SUFFIX);
//copy the class custom attributes
foreach (CustomAttributeBuilder attrBuilder in CreateCustomAttributeBuilder(objectToProxy.GetType()))
{
typeBuilder.SetCustomAttribute(attrBuilder);
}
//create two fields, one to store the proxied object, and one to store the Interceptor delegate
//this will also create a constructor to set both these values
FieldInfo[] fieldInfo = typeBuilder.CreateFieldsAndConstrucutor(
typeof(I), "ProxiedObject",
typeof(EmitProxyInterceptor <I>), "Interceptor");
//Create an implementation of each method in the interface. There is a direct implementation
//to conform to the interface, and an execute method that will call the proxied object directly
//given an object and a parameter list
foreach (MethodInfo interfaceMethodInfo in typeof(I).GetAllInterfaceMethods())
{
//get a list of parameter types
ParameterInfo[] parameterInfos = interfaceMethodInfo.GetParameters();
Type[] parameterTypes = new Type[parameterInfos.Length];
for (int i = 0; i < parameterInfos.Length; i++)
{
parameterTypes[i] = parameterInfos[i].ParameterType;
}
//get the method info of the actual object, it might have the attributes we are looking
MethodInfo proxiedMethodInfo = objectToProxy.GetType().GetMethod(interfaceMethodInfo.Name, parameterTypes);
//will only create proxy to call delegate if it contains the attribute we are looking for
//(note that either the itnerface or the actual object we are proxing can have the attribute)
//or no attribute was defined
MethodBuilder proxyMethod;
if (methodSelector(proxiedMethodInfo))
{
MethodInfo executeMethod = typeBuilder.CreateExecuteMethod <I>(EXECUTE_PREFIX + interfaceMethodInfo.Name, interfaceMethodInfo);
proxyMethod = typeBuilder.CreateProxyMethod <I>(interfaceMethodInfo, executeMethod, fieldInfo[0], fieldInfo[1]);
}
else
{
proxyMethod = typeBuilder.CreatePassThroughMethod <I>(interfaceMethodInfo, fieldInfo[0]);
}
//Copy accross the attributes
foreach (CustomAttributeBuilder attrBuilder in CreateCustomAttributeBuilder(proxiedMethodInfo))
{
proxyMethod.SetCustomAttribute(attrBuilder);
}
}
return(typeBuilder.CreateType());
}
/// <summary>
/// Creates a proxy for this object
/// </summary>
/// <typeparam name="I">Interface to proxy</typeparam>
/// <param name="objectToProxy"></param>
/// <param name="interceptorDelegate">delegate to call on method invocation</param>
/// <returns></returns>
public static I Proxy <I>(this I objectToProxy, EmitProxyInterceptor <I> interceptorDelegate)
{
return(PlatformTypeProxyCsharpHelper.Proxy <I>(objectToProxy, (info) => true, interceptorDelegate));
}
