How to use class name as parameter in C#
what i want to do is to automatically create some object.
In Java, class can be pass as parameter, for example
Class A{
}
Object createObjectBy(class clazz){
// .. do construction work here
}
when using it, just ---> cr开发者_高级运维eateObjectBy(A.class)
it is benefit for a lot of things.
so, how can i do similar thing in C#????
Object createObjectBy(Type clazz){
// .. do construction work here
Object theObject = Activator.CreateInstance(clazz);
return theObject;
}
Usage:
createObjectBy(typeof(A));
Or you could simply use Activator.CreateInstance
directly :-)
The ideal way would be to use generics
Type is known at design time
public static T CreateInstance<T>() where T: new()
{
// Do some business logic
Logger.LogObjectCreation(typeof(T));
// Actualy instanciate the object
return new T();
}
A call example would look like
var employee = CreateInstance<Employee>();
Type is unknown at runtime
If the type of object is unknown at runtime, for example through a plugin system, you need to use the Type
class:
public static object CreateInstance(Type type)
{
// Do some business logic
Logger.LogObjectCreation(type);
// Actualy instanciate the object
return Activator.CreateInstance(type);
}
A call example would look like
var instance = CreateInstance(someType);
Performance
Of course, nothing beats instanciating an object than by using the keyword new
. Except maybe not instanciating, but instead reusing an object, like through caching.
If you have to settle for the second method where the type is unknown, there are some alternatives to Activator.CreateInstance
. Although the article recommend using lambda expression, your biggest consideration is:
- Does your unknown object need to be instantiated often in a short period of time, or do you only create it once
If you only need to create your object once, just stick with the Activator.CreateInstance method. If you need to create it multiple time in a short time, try the lambda approach. That last approach is similar to a compiled regular expression vs. an on-the-fly regular expression.
C# doesn't support this. But what are you trying to do?
You probably could use:
createObjectBy(Type type);
or
createObjectBy<T>();
Use the class Type. You can return an instance of it by call
obj.GetType();
or without an object instance
typeof(className);
I hope it helps.
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