Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
608 views
in Technique[技术] by (71.8m points)

c# - Activator.CreateInstance(string) and Activator.CreateInstance<T>() difference

No, this is not a question about generics.

I have a Factory pattern with several classes with internal constructors (I don't want them being instantiated if not through the factory).

My problem is that CreateInstance fails with a "No parameterless constructor defined for this object" error unless I pass "true" on the non-public parameter.

Example

// Fails
Activator.CreateInstance(type);

// Works
Activator.CreateInstance(type, true);

I wanted to make the factory generic to make it a little simpler, like this:

public class GenericFactory<T> where T : MyAbstractType
{
    public static T GetInstance()
    {
        return Activator.CreateInstance<T>();
    }
}

However, I was unable to find how to pass that "true" parameter for it to accept non-public constructors (internal).

Did I miss something or it isn't possible?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

To get around this, couldnt you just alter your usage as such:

public class GenericFactory<T> where T : MyAbstractType
{
    public static T GetInstance()
    {
        return Activator.CreateInstance(typeof(T), true);
    }
}

Your factory method will still be generic, but the call to the activator will not use the generic overload. But you should still achieve the same results.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...