Cannot access static method in non-static context

问题

I've just recently started my intermediate course in C# programming and I'm learning how to create multiple classes and creating methods to use in my program.

It's a very new topic to me so I apologize if it's something very obvious or stupid. I am getting below message in all of my methods:

Cannot access static method in non-static context

Code in method class:

public static int Add(params int[] numbers) {
        var sum = 0;

        foreach (var n in numbers) {
            sum += n;
        }

        return sum;
    }

    public static int Subtract(params int[] numbers) {
        var sum = 0;

        foreach (var n in numbers) {
            sum -= n;
        }

        return sum;
    }

    public static int Multiply(params int[] numbers) {
        var sum = 0;

        foreach (var n in numbers) {
            sum *= n;
        }

        return sum;
    }

    public static int Divide(params int[] numbers) {
        var sum = 0;

        foreach (var n in numbers) {
            sum /= n;
        }

        return sum;
    }

    public static string[] CheckingOfSomeSort(string userInput, int value, bool isAddition, bool isSubtraction, bool isDivision, bool isMultiplication) {
        if (userInput.Contains("+")) {
            var addition = userInput.Split('+');
            value = 1;
            isAddition = true;
            return addition;
        } else if (userInput.Contains("-")) {
            var subtraction = userInput.Split('-');
            value = 2;
            isSubtraction = true;
            return subtraction;
        } else if (userInput.Contains("*")) {
            var multiplication = userInput.Split('*');
            value = 3;
            isMultiplication = true;
            return multiplication;
        } else if (userInput.Contains("/")) {
            var division = userInput.Split('/');
            value = 4;
            isDivision = true;
            return division;
        }

        return null;
    }

I am attempting to create a calculator (which I have already done, however I'm trying to use methods now)

回答1:

As per your comment I got to know that you are creating an object of CalculatorMethods and you are trying to call methods of that class which are static using this object.

My Comment on question:

these methods are static. (and the way they are used they should be static too). But static methods cannot be accessed with object of Class but with directly Type of the class. here I m guessing CalculatorMethods is class in which methods are and you will try to do something like calc.Add() .. which will not be possible . Instead do CalculatorMethods.Add()

Instead you can try it by calling with Type directly like belwo,

    void MethodOfCalling()
    {
        int sum = CalculatorMethods.Add(new int[2] { 1, 2 });
    }

you can see, I have used CalculatorMethods (a class name - more properly saying Type of the class) to call method not object of the class.

回答2:

@MrSanfrinsisco, Welcome to C# programming. As you ask its very easy to call static methods. to make a call follow the below steps

1) create 1 class file . Lets say its Calculations.cs [put your code inside this class] final layopout of your class will be..

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace WebApplication3.Models
{
    public class Calculations
    {
        public static int Add(params int[] numbers)
        {
            var sum = 0;

            foreach (var n in numbers)
            {
                sum += n;
            }

            return sum;
        }

        public static int Subtract(params int[] numbers)
        {
            var sum = 0;

            foreach (var n in numbers)
            {
                sum -= n;
            }

            return sum;
        }

        public static int Multiply(params int[] numbers)
        {
            var sum = 0;

            foreach (var n in numbers)
            {
                sum *= n;
            }

            return sum;
        }

        public static int Divide(params int[] numbers)
        {
            var sum = 0;

            foreach (var n in numbers)
            {
                sum /= n;
            }

            return sum;
        }

        public static string[] CheckingOfSomeSort(string userInput, int value, bool isAddition, bool isSubtraction, bool isDivision, bool isMultiplication)
        {
            if (userInput.Contains("+"))
            {
                var addition = userInput.Split('+');
                value = 1;
                isAddition = true;
                return addition;
            }
            else if (userInput.Contains("-"))
            {
                var subtraction = userInput.Split('-');
                value = 2;
                isSubtraction = true;
                return subtraction;
            }
            else if (userInput.Contains("*"))
            {
                var multiplication = userInput.Split('*');
                value = 3;
                isMultiplication = true;
                return multiplication;
            }
            else if (userInput.Contains("/"))
            {
                var division = userInput.Split('/');
                value = 4;
                isDivision = true;
                return division;
            }

            return null;
        }
    }
}

2) then go to the page inside which you want to access that method and simply write. Here for example if you want to use it on default.aspx then use below method. [Note: you must give name space of your class here then only you are able access this class in my example it is, using WebApplication3.Models;]

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using WebApplication3.Models;

namespace WebApplication3
{
    public partial class Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            int resultAdd= Calculations.Add(new int[3] { 1, 2, 3 });
            int resultSubstract= Calculations.Subtract(new int[3] { 1, 2, 3 });
            int resultDivide= Calculations.Divide(new int[3] { 1, 2, 3 });
            int resultMultiply=Calculations.Multiply(new int[3] { 1, 2, 3 });
        }

    }
}

this is the basic notes to call such kind of methods.

Let me know still you need any help. :)

回答3:

To call the static method you need to refer to it from the class it's defined in, not an instance of that class. eg :

Calculator.Divide(); // works 


Calculator obj = new Calculator(); 
obj.Divide(); // Not works

NOTE : Divide() is a static method

来源：https://stackoverflow.com/questions/50576163/cannot-access-static-method-in-non-static-context