C# object reference question

Question

I am creating a really basic program, that has a method to fill an array but I am getting an error I don't understand. I am a Java programmer trying to acclimate to C# and .NET. Any help would be great.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.Threading;

namespace TestThreads
{
    class Program
    {
        static void Main(string[] args)
        {
             int[]  empty = new int[50001];
             int[] filled = new int[50001];

            filled = compute(empty); //error occurs here

            Console.ReadLine();
        }

        public int[] compute(int[] inArray)
        {
            for (int i = 0; i < inArray.Length; i++)
            {
                inArray[i] = i << 2;
            }

            return inArray;
        }
    }
}

Error Message:

Error 1 An object reference is required for the non-static field, method, or property 'TestThreads.Program.compute(int[])' C:\Users\hunter.mcmillen\Desktop\TestProcessSplitting\TestProcessSplitting\Program.cs 17 22 TestThreads

Thanks, Hunter

Java would give you a similar error in that case... you're trying to call an instance method as if it was static. — Thomas Levesque
– Thomas Levesque, Commented Jun 3, 2011 at 14:55
correct, but the Java compiler gives me this message: non-static method compute(int[]) cannot be referenced from a static context, which I can actually understand. — Hunter McMillen
– Hunter McMillen, Commented Jun 3, 2011 at 14:57

psousa · Accepted Answer · 2011-06-03 14:53:05Z

6

The compute method should be static.

public static int[] compute(int[] inArray)

answered Jun 3, 2011 at 14:53

psousa

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Comments

JaredPar · Accepted Answer · 2011-06-03 14:53:45Z

6

You're trying to call compute which is an instance method from Main which is a static method. To fix this make compute static as well`

public static int[] compute(int[] inArray)

answered Jun 3, 2011 at 14:53

JaredPar

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Comments

Marc Gravell · Accepted Answer · 2011-06-03 14:54:35Z

2

Main is a static method - it is not specific to any single object - indeed, no instance of Program is created to call Main. compute is an instance method, and needs to be invoked on a single object.

Two options:

make compute static, which makes sense since it uses no state (fields):
```
public static int[] compute(int[] inArray) {...}
```

create an instance in Main:

var obj = new Program();
filled = obj.compute(empty);

The first is more appealing here. I've included the second purely for completeness.

answered Jun 3, 2011 at 14:54

Marc Gravell

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Comments

Bala R · Accepted Answer · 2011-06-03 14:53:21Z

1

Change public int[] compute(int[] inArray){...}

to

public static int[] compute(int[] inArray){..}

or change your call from

filled = compute(empty);

to

filled = new Program().compute(empty);

The compute() method that you have is an instance (non-static) method and requires an instance to be invoked.

answered Jun 3, 2011 at 14:53

Bala R

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Comments

Khepri · Accepted Answer · 2011-06-03 14:54:09Z

0

Add static to the compute method declaration.

public static int[] compute(int[] inArray)

answered Jun 3, 2011 at 14:54

Khepri

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Comments

myermian · Accepted Answer · 2011-06-03 14:54:41Z

0

You're method is not static, but is being referenced from a static method. Change it to static. Solved.

public static int[] compute(int[] inArray) { ... }

answered Jun 3, 2011 at 14:54

myermian

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