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Hey guys

I know that when an object is static only one of that object can exist at any given time. I also know that if a class is static I don't need to instantiate it to use it which is very useful :)

What i don't get is why is it useful to have a static variable inside of an instantiate-able class?

Example:
public class Foo
{
    public Foo(int Bar)
    {
        bar = Bar;
    }

    private static int bar;
    public static int Bar
    {
        get { return bar; }
        set { bar = value; }
    }
}


Thanks
Posted

Generally, if you want multiple objects of the same type to share data. For example, you might have a static RootNode member, if all your objects need to refer to it - that way you only need to initialise it once for the whole class, rather than per-instance
 
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Every info that has to be shared by all the instances (or none of them) of the class could be a good candidate.
For instance if you want to count how many instances (pardon the pun) of the class were created.
:)
 
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v2
Another example is a Message class in which each instance has a unique ID that is the previously assigned ID + 1;
 
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Thread safety can make heavy use of a static variable. If you are aiming to lock a section, it makes sense for the variable to be static so that you achieve the aim of locking based on one object. For instance:
private static readonly object _syncLock = new object();

public void CriticalProcess()
{
  lock(_syncObject)
  {
    // Do something critical here.
  }
}
 
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wrote:
What i don't get is why is it useful to have a static variable inside of an instantiate-able class?


Think about string.Empty. Empty is a public static field on class System.String. It is often used when you implement singleton design pattern.
 
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wrote:
why is it useful


IMO, its not (unless you want a counter of some sort).
 
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v2

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