Error an object reference is required for the non-static field method or property

Question

I m creating an application in C   Its function is to evaluate if a given  is prime and if the same swapped number is prime as well   When I build my solution in Visual Studio  it says that  an object reference is required for the non-static field  method or property      I m having this problem with the  volteado  and  siprimo  methods   Where is the problem and how can I fix it   namespace ConsoleApplication1       class Program               static void Main string   args                        Console Write  Write a number                  long a  Convert ToInt64 Console ReadLine        a is the number given by the user               long av   volteado a      av is  a  but swapped              if  siprimo a     false  amp  amp  siprimo av     false                  Console WriteLine  Both original and swapped numbers are prime                 else                 Console WriteLine  One of the numbers isnt prime                 Console ReadLine                       private bool siprimo long a                           Evaluate if the received number is prime             bool sp   true              for  long k   2  k  lt   a   2  k                    if  a   k    0  sp   false              return sp                     private long volteado long a                           Swap the received number             long v   0              while  a  gt  0                                v   10   v   a   10                  a    10                            return v

User · Accepted Answer

You can t access non-static members from a static method   Note that Main   is static  which is a requirement of  Net   Just make siprimo and volteado static  by placing the static keyword in front of them  e g     static private long volteado long a

User · Answer

The error message means that you need to invoke volteado and siprimo on an instance of the Program class   E g        Program p   new Program    long av   p volteado a      av is  a  but swapped  if  p siprimo a     false  amp  amp  p siprimo av     false        They cannot be invoked directly from the Main method because Main is static while volteado and siprimo are not   The easiest way to fix this is to make the volteado and siprimo methods static   private static bool siprimo long a               private static bool volteado long a

User · Answer

Create a class and put all your code in there and call an instance of this class from the Main     static void Main string   args         MyClass cls    new MyClass        Console Write  Write a number          long a  Convert ToInt64 Console ReadLine        a is the number given by the user     long av   cls volteado a       bool isTrue   cls siprimo a             etc

User · Answer

You just need to make the siprimo and volteado methods static   private static bool siprimo long a    and  private static long volteado long a

User · Answer

Change your signatures to private static bool siprimo long a  and private static long volteado long a  and see where that gets you

User · Answer

Simply add static in the declaration of these two methods and the compile time error will disappear   By default in C  methods are instance methods  and they receive the implicit  self  argument  By making them static  no such argument is needed  nor available   and the method must then of course refrain from accessing any instance  non-static  objects or methods of the class   More info on static methods Provided the class and the method s access modifiers  public vs  private  are ok  a static method can then be called from anywhere without having to previously instantiate a instance of the class   In other words static methods are used with the following syntax       className classMethod arguments  rather than     someInstanceVariable classMethod arguments    A classical example of static methods are found in the System Math class  whereby we can call a bunch of these methods like     Math Sqrt 2     Math Cos Math PI    without ever instantiating a  Math  class   in fact I don t even know if such an instance is possible

[c#] Error: "an object reference is required for the non-static field, method or property..."

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