Activator

Activator

CF 1.0

---

System (mscorlib.dll)

sealed class

This class is used to activate objects; that is, it either creates an object or obtains a handle to an existing object. This class is generally used in a variety of specialized conditions. For example, Activator can create an object within another AppDomain and hold a handle to that object. This effectively gives a multidomain container application (such as ASP.NET) the ability to reach into another AppDomain to perform tasks within that domain (such as closing down the AppDomain in the event of a user request to shut down the application server).

Activator 's methods come in two distinct flavors: CreateInstance( ) and CreateInstanceFrom( ) . These create new objects when given particular criteria (such as the type to create and the assembly from which to create it). The GetObject( ) method uses published System.Runtime.Remoting.RemotingConfiguration data to locate another object and obtain a handle to it (usually in preparation for some remote-object method invocations).

All of the methods in Activator return a System.Runtime.Remoting.ObjectHandle , not the actual object itself; this object is actually a proxy to the created/remote object. As such, programmers must call Unwrap( ) on the returned ObjectHandle to use the object. (Note that an explicit downcast is required, since the return value is declared to be a generic object .)

Figure 26-5. Value types in the System namespace

 public sealed class  Activator  {  // Public Static Methods  public static ObjectHandle  CreateComInstanceFrom  (string   assemblyName   , string   typeName   );    public static ObjectHandle  CreateComInstanceFrom  (string   assemblyName   , string   typeName   ,          byte[ ]   hashValue   , System.Configuration.Assemblies.AssemblyHashAlgorithm   hashAlgorithm   );    public static object  CreateInstance  (Type   type   );    public static object  CreateInstance  (Type   type   , System.Reflection.BindingFlags   bindingAttr   ,          System.Reflection.Binder   binder   , object[ ]   args   , System.Globalization.CultureInfo   culture   );    public static object  CreateInstance  (Type   type   , System.Reflection.BindingFlags   bindingAttr   ,           System.Reflection.Binder   binder   , object[ ]   args   , System.Globalization.CultureInfo   culture   ,          object[ ]   activationAttributes   );    public static object  CreateInstance  (Type   type   , bool   nonPublic   );    public static object  CreateInstance  (Type   type   , object[ ]   args   );    public static object  CreateInstance  (Type   type   , object[ ]   args   , object[ ]   activationAttributes   );    public static ObjectHandle  CreateInstance  (string   assemblyName   , string   typeName   );    public static ObjectHandle  CreateInstance  (string   assemblyName   , string   typeName   , bool   ignoreCase   ,          System.Reflection.BindingFlags   bindingAttr   , System.Reflection.Binder   binder   , object[ ]   args   ,          System.Globalization.CultureInfo   culture   , object[ ]   activationAttributes   ,          System.Security.Policy.Evidence   securityInfo   );    public static ObjectHandle  CreateInstance  (string   assemblyName   , string   typeName   , object[ ]   activationAttributes   );    public static ObjectHandle  CreateInstanceFrom  (string   assemblyFile   , string   typeName   );    public static ObjectHandle  CreateInstanceFrom  (string   assemblyFile   , string   typeName   , bool   ignoreCase   ,          System.Reflection.BindingFlags   bindingAttr   , System.Reflection.Binder   binder   , object[ ]   args   ,          System.Globalization.CultureInfo   culture   , object[ ]   activationAttributes   ,          System.Security.Policy.Evidence   securityInfo   );    public static ObjectHandle  CreateInstanceFrom  (string   assemblyFile   , string   typeName   ,     object[ ]   activationAttributes   );    public static object  GetObject  (Type   type   , string   url   );    public static object  GetObject  (Type   type   , string   url   , object   state   ); }