C# Random console math equation game: Converting string back to equation?

Question

I'm currently teaching myself C# and came up with a program idea as follows:

1. Program generates random number
2. Program generates random math operator
3. Program generates random number
4. Asks user for the answer to the randomly generated problem
5. User inputs answer
6. Program compares result of generated problem against user's input
7. Program prints whether user was correct or incorrect.

The issue I'm running into is that I can only print the equation in the following format/data types:

(example) 5 + 1 (number, string operator, number)

OR combine the above data types into a single string

From there the problem is that I cannot figure out how to convert all of it into a math equation that can be stored in a variable and then compared against the user's input.

I'm sure I'm making it more difficult than it probably is, but I've been at this program, forums, and tons of posts without being able to piece anything together.

Any insight to my code and where I'm going wrong would be greatly appreciated in my learning C#!

public static void Main(string[] args)
{
    mathProblem();
    int userAnswer = Convert.ToInt32(Console.ReadLine());
}

public static void mathProblem()
{
    Random numberGenerator = new Random();
    Random operatorSelect = new Random();

    //Generates random number for 1st part of problem
    int number1 = numberGenerator.Next(1, 11);
    //Generates random number for 2nd part of problem
    int number2 = numberGenerator.Next(1, 11);
    //int to store/assign random operator
    int mathOperator = 0;
    //newOperator set to empty string that will change and store operator generated
    string newOperator = "";

    // gives value of 1-4
    mathOperator = operatorSelect.Next(5);
    switch (mathOperator)
    {
        case 1:
            newOperator = "+";
            break;
        case 2:
            newOperator = "-";
            break;
        case 3:
            newOperator = "*";
            break;
        case 4:
            newOperator = "/";
            break;
        default:
            newOperator = "+"; 
            break;
    }

    Convert.ToString(number1);
    Convert.ToString(number2);

    Console.WriteLine("What is " + number1 + " " + newOperator + " " + number2 + "?");
}

Answer 1

Arithmetic operations are functions that accept two numbers and return a third number. In general they can be expressed as a function:

int AddOperation(int a, int b)
{
    return a + b;
}

A delegate for this sort of function can be stored in a variable that is typed as a Func<int,int,int>.

Func<int,int,int> functionPointer = AddOperation;

Instead of declaring a whole method just for AddOperation, you can also store it is an anonymous method declared with a lambda expression:

Func<int,int,int> functionPointer = (a,b) => a + b;

And you can store a series of these functions, for example, in a dictionary:

var operators = new Dictionary<string,Func<int,int,int>>
{
    { "+", (a,b) => a + b },
    { "-", (a,b) => a - b },
    { "*", (a,b) => a * b },
    { "/", (a,b) => a / b }
};

Then to execute an operation, you look up the function:

var symbol = "+";
var operation = operators[symbol];

...and use it to compute the result:

var result = operation(arg1,arg2);

Here is an example that performs all four operations on the numbers 10 and 2:

public static void Main()
{
    var operators = new Dictionary<string,Func<int,int,int>>
    {
        { "+", (a,b) => a + b },
        { "-", (a,b) => a - b },
        { "*", (a,b) => a * b },
        { "/", (a,b) => a / b }
    };

    var arg1 = 10;
    var arg2 = 2;

    foreach (var symbol in operators.Keys)
    {
        var func = operators[symbol];
        var result = func(arg1,arg2);
        Console.WriteLine("{0}{1}{2}={3}", arg1, symbol, arg2, result);
    }
}

Output:

10+2=12
10-2=8
10*2=20
10/2=5

Link to working example on DotNetFiddle

Answer 2

I think you are going about this in the wrong direction. Why do you need to store the operator as a string? Why have all these separate random instances? At the end of the day you need to randomly generate a math problem right? And you have to determine if the user gets the answer correct or not.

So first things first, use a single static Random field instead of a local variable:

private static Random rnd = new Random();

public static void GenerateRandomMathProblem()
{
    // code
}

See here for some good info on why you dont want to use multiple Random variables like you were.

Also consider a better name than mathProblem(), use something more descriptive (What about a math problem?) also use the proper casing (PascalCase).

Second issue: the variables you track. I think you should only care about these variables:

int number1 = rnd.Next(1, 11);

int number2 = rnd.Next(1, 11);

// Store the answer, has to be a double since you have some division operation
double answer = 0;

// Store the question so you can ask the user
string question = string.Empty;

Now, your switch case has to perform double duty. Perform the actual math and store the result in answer and generate the actual string question and assign to to question

// Case of '-'
case 1:
    answer = number1 - number2; //Gets the answer
    question = $"{number1} - {number2}"; //Syntax is called string interpolation, its a little cleaner than concatenation
    break;

We have already generated the question so we dont need the number variables anymore, but just so you are aware, the Convert calls you do are completely unnecessary. Console.WriteLine() will automatically call ToString() on its arguments. And every single thing in C# can have .ToString() called on it since its a member of object and everything in C# inherits from System.Object:

Now, at the end when you ask your question, instead of using string concatenation you can use the "formatting" capability of Console.WriteLine() to make your code a bit cleaner:

// The {0} will be replaced with the value of 'question' in the console
Console.WriteLine("What is {0}?", question);