private & static member

Question

hi, how can i use private and static member in c# ? thanks...

Vulpes · Answer

Here's an example which uses a private static field to store the number of instances of a class which have been created but not yet destroyed. The field is exposed to code outside the class using a public read-only property: using System; using System.Threading; class MyClass { private static int counter; public static int Counter { get { return counter; } } public MyClass() { counter++; } ~MyClass() { counter--; } } class Test { static void Main() { MyClass mc = new MyClass(); MyClass mc2 = new MyClass(); Console.WriteLine(MyClass.Counter); // 2 mc = null; mc2 = null; GC.Collect(); Thread.Sleep(1000); Console.WriteLine(MyClass.Counter); // 0 Console.ReadKey(); } }

Vulpes · Answer

A static constructor is never called directly in code but by the system (once and once only) when any static member or instance constructor of the class is first accessed. It can't take parameters and is generally used to initialize static fields in ways which can't be done simply by assigning them constants when they're declared. So, are you now wanting to make all your fields static rather than instance?

Orhan SALUR · Answer

if my constructor would be static how can i write?

Vulpes · Answer

Well, as your fields are private, you can't set them directly but could set them via a constructor, say. You could then call the x() method to print them out: using System; class MyClass { private string name; private string surname; private int number; public MyClass(string name, string surname, int number) { this.name = name; this.surname = surname; this.number = number; } public void x() { Console.WriteLine(name + " " + surname + " " + number); } } class Test { static void Main() { MyClass mc = new MyClass("Orhan","SALUR", 123456); mc.x(); Console.ReadKey(); } }

Orhan SALUR · Answer

using System; class MyClass { private string name; private string surname; private int number; public object x(string n, string s, int no) { name = n; surname = s; number = no; // return 0; } public void show() { Console.WriteLine(mc.n + mc.s + mc.no); } } class program { static void Main() { MyClass mc new MyClass(); mc.n="Orhan"; mc.s="SALUR"; mc.no=123456; mc.show(); Console.ReadKey(); } }

Orhan SALUR · Answer

oke thanks... using System; class MyClass { private string name; private string surname; private int number; public x() } class Test { static void Main() { MyClass mc new MyClass(); mc.name="Orhan"; mc.surname="SALUR"; mc.number=123456; Console.WriteLine(mc.name+mc.surname+mc.number); Console.ReadKey(); } } how can i write x() method?

Vulpes · Answer

Yes, you can. In fact instance fields are normally declared as private and then exposed to outside code via a public property. To access a private instance field using reflection, you'll need to change the BindingFlags variable to: BindingFlags bf = BindingFlags.Instance | BindingFlags.NonPublic; and then pass an object reference to the FieldInfo.GetValue method.

Orhan SALUR · Answer

can we use privete member without static? ex: class test { private string name; private string surname; private int number; }

Vulpes · Answer

You can use reflection to access a private static member from code outside the class. Suppose in the original example, we don't have the public read-only property. Then, we can still get the value of 'counter' as follows: using System; using System.Threading; using System.Reflection; class MyClass { private static int counter; public MyClass() { counter++; } ~MyClass() { counter--; } } class Test { static void Main() { MyClass mc = new MyClass(); MyClass mc2 = new MyClass(); Type t = typeof(MyClass); BindingFlags bf = BindingFlags.Static | BindingFlags.NonPublic; FieldInfo fi = t.GetField("counter", bf); Console.WriteLine(fi.GetValue(null)); // 2 mc = null; mc2 = null; GC.Collect(); Thread.Sleep(1000); Console.WriteLine(fi.GetValue(null)); // 0 Console.ReadKey(); } } Notice that, as there's no object with a static member (it belongs to the class as a whole), we need to pass a null argument to the FieldInfo.GetValue member.

Orhan SALUR · Answer

also how can we access private members?