Reflection#
Is the ability to inspect and change information about assemblies, types and code at runtime. Is used for plugin development, logging, code analysis etc. Assemblies contain modules => Modules contain types => Types contain code
var a = Assembly.LoadFrom("MyAssembly.dll");
var b = Assembly.GetExecutingAssembly();
// List all types in assembly
Type[] types = a.GetTypes();
foreach (var t in types)
Console.WriteLine(t.FullName);
Type t = assembly.GetType("Namespace.SomeClass");
foreach (MethodInfo m in t.GetMethods())
Console.WriteLine(m.Name);
object o = a.CreateInstance("MyPlugin.HelloWorld");
Type hwClass = a.GetType("MyPlugin.MethodInfo");
MethodInfo mi = hwClass.GetMethod("ToString"); // by default only public
MethodInfo mi = hwClass.GetMethod("SayItPrivate", BindingFlags.Instance |
BindingFlags.NonPublic);
object retVal = mi.Invoke(o, null);
// Does class implement interface?
Type type = assembly.GetTypes () // scan all types
.Where(t => t.IsClass) // it must by a class , that
.Single(t => t.GetInterface("IMyInterface" != null ); // implements my interface
IMyInterface myObj = assembly.CreateInstance(type.FullName) as IMyInterface;
// call method
double res = myObj.DoSomething("input", 20);
System.Type#
Represents type declarations: class types, interface types, array and value types, enumeration types, type parameters, and more. Value, Interface or Class? => IsValueType , IsInterface , IsClass Public, Private or Sealed => IsNotPublic , IsSealed Abstract or Implementation? => IsAbstract
Attributes#
[Serializable]
class C {...} // marks the class as serializable
// will force compiler to produce a message
public class ObsoleteAttribute : Attribute
{
public string Message { get {...}
public bool IsError { get {...} set {...}
public ObsoleteAttribute() {...}
public ObsoleteAttribute(string msg) {...}
public ObsoleteAttribute(string msg , bool error) {...}
}
[Obsolete("Message Use class C1 instead", true)]
public class C {.. }
// Querying attributes at runtime
Type t = typeof(C);
object[] a = t.GetCustomAttributes(typeof(Comment), true);
Comment ca = (Comment)a[0];
Console.WriteLine(ca.Text + ", " + ca.Author);
AttributeUsage#
public class AttributeUsageAttribute : Attribute{
public AttributeUsageAttribute(AttributeTargets validOn){...}
public bool AllowMultiple { get; set; } // default: false
public bool Inherited { get; set; } // default: true
public AttributeTargets ValidOn { get; set; } // default: All
public virtual Object TypeId {get;}
}
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Interface, AllowMultiple = false)]
public class MyAttribute : Attribute {...}