Examining class members through Types and Reflection in .NET C#

Here we saw different ways to get hold of a Type. You can use the Type object to extract different ingredients of a class such as methods, properties, events etc. through various methods. The name of the object that these methods return ends with “Info”, like FieldInfo, MethodInfo etc.

These Info classes all derive from the MemberInfo abstract base class. The Type object also derives from MemberInfo.

Say you have the following Customer class:

public class Customer
{
	private string _name;

	public Customer(string name)
	{
		if (string.IsNullOrEmpty(name)) throw new ArgumentNullException("Customer name!");
		_name = name;
	}

	public string Name
	{
		get
		{
			return _name;
		}
	}
	public string Address { get; set; }
	public int SomeValue { get; set; }

	public int ImportantCalculation()
	{
		return 1000;
	}

	public void ImportantVoidMethod()
	{
	}

        public enum SomeEnumeration
	{
		ValueOne = 1
		, ValueTwo = 2
	}

	public class SomeNestedClass
	{
		private string _someString;
	} 
}

Let’s see how we can find these elements:

Type customerType = typeof(Customer);

FieldInfo[] fields = customerType.GetFields();
Console.WriteLine("Fields: ");
foreach (FieldInfo fi in fields)
{
	Console.WriteLine(fi.Name);
}

Console.WriteLine("Constructors: ");
ConstructorInfo[] constructors = customerType.GetConstructors();
foreach (ConstructorInfo ci in constructors)
{
	Console.WriteLine(ci.Name);
}

Console.WriteLine("Methods: ");
MethodInfo[] methods = customerType.GetMethods();
foreach (MethodInfo mi in methods)
{
	Console.WriteLine(mi.Name);
}

Console.WriteLine("Nested types: ");
Type[] nestedTypes = customerType.GetNestedTypes();
foreach (Type t in nestedTypes)
{
	Console.WriteLine(t.Name);
}

Console.WriteLine("Properties: ");
PropertyInfo[] properties = customerType.GetProperties();
foreach (PropertyInfo pi in properties)
{
	Console.WriteLine(pi.Name);
}

Console.WriteLine("Members: ");
MemberInfo[] members = customerType.GetMembers();
foreach (MemberInfo mi in members)
{
	Console.WriteLine("Type: {0}, name: {1}", mi.Name, mi.MemberType);
}

This will produce the following output:

You’ll notice a couple of things:

• We have a field called _name but it wasn’t picked up by the GetFields method. That’s because it’s a private variable. If you want to extract private fields and members then the BindingFlags enumeration will come in handy – we’ll look at that in a separate post. The default behaviour is that you’ll only see the public members of a class. This is true for both static and instance members.
• The get-set properties were translated into methods like get_Name and set_SomeValue
• The methods inherited from Object were also included in the MethodInfo array – all public methods of the base class will be picked up by GetMethods()
• GetMembers returns every public member of a class in a MemberInfo array. As noted above each Info class derives from MemberInfo. MemberInfo will contain some common functionality for all derived Info classes, like the Name property, but for anything specific to any derived Info class you’ll need to inspect the derived class of course

Another base class which is important to know of is MethodBase which also derives from MemberInfo. It represents any member that can contain a body: constructors and methods which in turn are represented by ConstructorInfo and MethodInfo.

View all posts on Reflection here.