Accessing class member from static method

Question

I know there are a lot of threads talking about this but so far I haven't found one that helps my situation directly. I have members of the class that I need to access from both static and non-static methods. But if the members are non-static, I can't seem to get to them from the static methods.

public class SomeCoolClass
{
    public string Summary = "I'm telling you";

    public void DoSomeMethod()
    {
        string myInterval = Summary + " this is what happened!";
    }

    public static void DoSomeOtherMethod()
    {
        string myInterval = Summary + " it didn't happen!";
    }
}

public class MyMainClass
{
    SomeCoolClass myCool = new SomeCoolClass();
    myCool.DoSomeMethod();

    SomeCoolClass.DoSomeOtherMethod();
}

How would you suggest I get Summary from either type of method?

Static members belong to the *Type* Non-static members belong to an *instance of that type*. — asawyer, Aug 10 '12 at 17:48
Do you need `Summary` to be constant? You can mark is `public const string Summary` and you can access it from both. — Justin Skiles, Aug 10 '12 at 17:48

score 9 · Accepted Answer · answered Aug 10 '12 at 17:48

9

How would you suggest I get Summary from either type of method?

You'll need to pass myCool to DoSomeOtherMethod - in which case you should make it an instance method to start with.

Fundamentally, if it needs the state of an instance of the type, why would you make it static?

answered Aug 10 '12 at 17:48

Jon Skeet

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Thanks guys for your constructive advice. I realized, after I submitted the question and headed off to lunch that it would just save me some hassle if I made DoSomeOtherMethod an instance method and be done with it. – Jeremy Aug 10 '12 at 18:11

score 7 · Answer 2 · answered Aug 10 '12 at 17:48

7

You can't access instance members from a static method. The whole point of static methods is that they're not related to a class instance.

answered Aug 10 '12 at 17:48

Manu Clementz

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score 2 · Answer 3 · answered Aug 10 '12 at 17:59

You simply can't do it that way. Static methods cannot access non static fields.

You can either make Summary static

public class SomeCoolClass
{
    public static string Summary = "I'm telling you";

    public void DoSomeMethod()
    {
        string myInterval = SomeCoolClass.Summary + " this is what happened!";
    }

    public static void DoSomeOtherMethod()
    {
        string myInterval = SomeCoolClass.Summary + " it didn't happen!";
    }
}

Or you can pass an instance of SomeCoolClass to DoSomeOtherMethod and call Summary from the instance you just passed :

public class SomeCoolClass
{
    public string Summary = "I'm telling you";

    public void DoSomeMethod()
    {
        string myInterval = this.Summary + " this is what happened!";
    }

    public static void DoSomeOtherMethod(SomeCoolClass instance)
    {
        string myInterval = instance.Summary + " it didn't happen!";
    }
}

Anyway I can't really see the goal you're trying to reach.

Accessing class member from static method

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