• It helps to access the metadata for types within an assembly, including constructs such as the full type name, member names.
• It allows to dynamically invoke a type’s member at runtime using the metadata.
• It lets developers to enumerate through all the types within an assembly and search for those that match certain criteria.
• Reflection has the following uses:
  • It allows view attribute information at runtime.
  • It allows examining various types in an assembly and instantiate these types.
  • It allows late binding to methods and properties.
  • It allows creating new types at runtime and then performs some tasks using those types.
• There are some provisions for reflecting on generic types.
  • Runtime reflection on generics determines whether a class or method contains a generic type, and any type parameters or arguments it may include.

Load Assembly

• If you call Assembly.Load() multiple times, the runtime will load the assembly only once.
• If you want to reload the assembly you would have to restart the application.

var typeAssembly = Assembly.GetAssembly(typeof(IMyInterface));
var callingAssembly = Assembly.GetCallingAssembly();
var entryAssembly = Assembly.GetEntryAssembly();
var executingAssembly = Assembly.GetExecutingAssembly();
var pluginAssembly = Assembly.Load("AssemblyName");

// Must use fully qualified name (including namespace) and cast to the target object:
var newInstanceByName = pluginAssembly.CreateInstance("MyNameSpace.MyClassName");

var interfaces = pluginAssembly.GetTypes()
    .Where(x => typeof(IMyInterface).IsAssignableFrom(x) && !x.IsInterface);
foreach (Type interfaceType in interfaces)
{
    var newInstance = Activator.CreateInstance(interfaceType) as IMyInterface;
    newInstance.Action();
}

Accessing Metadata Using System.Type

• Reflection can also be used to inspect the value of a property or a field on one object instance.

FieldInfo[] fields = myObject.GetType().GetFields(BindingFlags.Instance | BindingFlags.NonPublic);
foreach (var field in fields)
    if (field.FieldType == typeof(int))
        Console.WriteLine(field.GetValue(myObject));

• Reflection can also be used to execute a method on a type.

int myNumber = 42;
MethodInfo compareToMethod = myNumber.GetType().GetMethod("CompareTo", new Type[] { typeof(int) });
int result = (int)compareToMethod.Invoke(myNumber, new object[] { 41 });

• The GetMethods() call does not return extension methods.
  • They are available only as static members on the type.

Member Invocation

• You can take the metadata and dynamically invoke the members it references.

PropertyInfo property = myObject.GetType().GetProperty("MyProperty",
    BindingFlags.IgnoreCase | BindingFlags.Instance | BindingFlags.Public);
if (property != null)
{
    if (property.PropertyType == typeof(bool))
        property.SetValue(myObject, true, null); // Last parameters for indexers
    else if (property.PropertyType == typeof(string))
        property.SetValue(myObject, "MyValue", null);
		Console.WriteLine(property.GetValue(myObject, "MyValue"));
}

Working with Generics

• You can determine whether a class or method contains generic parameters by querying the ContainsGenericParameters().
• You can get a list of generic arguments, or type parameters, from a generic class by calling the GetGenericArguments().
• The result is an array of Type instances that corresponds to the order in which they are declared in the generic class.

Type type = typeof(Nullable<>);
var hasGenericParameters = type.ContainsGenericParameters;
var isGenericType = type.IsGenericType;
Type[] genericArgumens = type.GetGenericArguments();