C# – Find a private field with Reflection

The name reflection is used to describe code which is able to inspect other code in the same system (or itself).

For example, say you have an object of an unknown type in Java, and you would like to call a 'doSomething' method on it if one exists. Java's static typing system isn't really designed to support this unless the object conforms to a known interface, but using reflection, your code can look at the object and find out if it has a method called 'doSomething' and then call it if you want to.

So, to give you a code example of this in Java (imagine the object in question is foo) :

Method method = foo.getClass().getMethod("doSomething", null);
method.invoke(foo, null);

One very common use case in Java is the usage with annotations. JUnit 4, for example, will use reflection to look through your classes for methods tagged with the @Test annotation, and will then call them when running the unit test.

There are some good reflection examples to get you started at http://docs.oracle.com/javase/tutorial/reflect/index.html

And finally, yes, the concepts are pretty much similar in other statically typed languages which support reflection (like C#). In dynamically typed languages, the use case described above is less necessary (since the compiler will allow any method to be called on any object, failing at runtime if it does not exist), but the second case of looking for methods which are marked or work in a certain way is still common.

Update from a comment:

The ability to inspect the code in the system and see object types is not reflection, but rather Type Introspection. Reflection is then the ability to make modifications at runtime by making use of introspection. The distinction is necessary here as some languages support introspection, but do not support reflection. One such example is C++

According to the StyleCop Rules Documentation the ordering is as follows.

Within a class, struct or interface: (SA1201 and SA1203)

• Constant Fields
• Fields
• Constructors
• Finalizers (Destructors)
• Delegates
• Events
• Enums
• Interfaces (interface implementations)
• Properties
• Indexers
• Methods
• Structs
• Classes

Within each of these groups order by access: (SA1202)

• public
• internal
• protected internal
• protected
• private

Within each of the access groups, order by static, then non-static: (SA1204)

• static
• non-static

Within each of the static/non-static groups of fields, order by readonly, then non-readonly : (SA1214 and SA1215)

• readonly
• non-readonly

An unrolled list is 130 lines long, so I won't unroll it here. The methods part unrolled is:

• public static methods
• public methods
• internal static methods
• internal methods
• protected internal static methods
• protected internal methods
• protected static methods
• protected methods
• private static methods
• private methods

The documentation notes that if the prescribed order isn't suitable - say, multiple interfaces are being implemented, and the interface methods and properties should be grouped together - then use a partial class to group the related methods and properties together.