Cannot implicitly convert type "string" to "int"

Since I'm still fairly new to C#, I decided to go back to the basics.

Here I have a fairly simple problem with a basic number game I'm programming in C#. Basically, the game will generate a random number and if the user guesses the correct number, it will state that the user has won. Otherwise, it tells the user that it must guess again and it restarts the program.

This is the source code so far. I have just one bug and it's the classic "cannot implicitly convert type "string" to "int" bug. "Guess" is a string, but the program has to decide whether it equals the randomly generated number. I tried implementing a ConvertToInt32 statement but it did nothing. Can anybody help me with this?

Code:

---

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            int number;
            string numberstring;
            string guess;
            Random rand;
            rand = new Random();

            number = rand.Next(1, 3);

        Start:
            do
            {
                Console.WriteLine("Guess the number from 1 to 3.");
                guess = Console.ReadLine();

                if (guess = number)
                {
                    Console.WriteLine("You've won.");
                }

                else
                {
                    Console.WriteLine("Sorry, guess again.");
                    goto Start;
                }
            } while (guess != "Q");
        }
    }
}

---

Couple of things.

First, you need to change if (guess = number)- at this moment you're trying to assign the value of number to guess. To test equality you have to use 2 equal signs, like this:

Code:

---

if (guess == number)

---

Now you can cast guess as an int. Use the int.TryParse method if casting doesn't work. It works like this:

Code:

---

int guess
int.TryParse(Console.ReadLine(), out guess);

---

HTH

So, it should look like this?

Code:

---

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            int number;
            int guess;
            int.TryParse(Console.ReadLine, out guess);
            Random rand;
            rand = new Random();

            number = rand.Next(1, 3);

        Start:
            do
            {
                Console.WriteLine("Guess the number from 1 to 3.");
                guess = Console.ReadLine();

                if (guess == number)
                {
                    Console.WriteLine("You've won.");
                }

                else
                {
                    Console.WriteLine("Sorry, guess again.");
                    goto Start;
                }
            } while (guess != "Q");
        }
    }
}

---

Why are you using the goto? This isn't basic. remove them. Your code should work fine.

I entered in the TryParse statement and ran the program. Apparently, it didn't fix the problem. I got the same error. Here's the code.

Code:

---

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            int number;
            int guess;
            int.TryParse(Console.ReadLine(), out guess);
            Random rand;
            rand = new Random();

            number = rand.Next(1, 90004);
            do
            {
                Console.WriteLine("Guess the number from 1 to 90004.");
                guess = Console.ReadLine();

                if (guess == number)
                {
                    Console.WriteLine("You've won.");
                }

                else
                {
                    Console.WriteLine("Sorry, guess again.");
                    goto Start;
                }
            } while (guess != number);
        }
    }
}

---

First, remove "goto Start;" - no need for that at all.

Second, tell us:
(1) Is this an exception or a compiler error? If it's an exception, what is the type of the exception?
(2) What is the exact error message?
(3) At what line of that code it occurs?

Make sure you post the exact code you're currently using, the one that produces the error.

This line

while (guess != "Q");

could have caused it, but you've replaced it in the code sample you posted last.
As far as I can tell, if you copied the code you pasted here (from your last post) into VS, it would work just fine (except for the goto).

Could be that you forgot to change the type of one of your variables, or something. Read the error message carefully, double click it to be taken to the problematic line, see if there are any strings that are being used together with integers.

The guess string must be converted to an int before the comparison takes place.
Here are a few hints:

Code:

---

                guess_str = Console.ReadLine();
                guess_str = guess_str.ToUpper();
                if (guess_str != "Q")
                {
                    guess_number = Convert.ToInt16(guess_str);

---

Some background reading on why goto is no longer used: http://www.u.arizona.edu/~rubinson/c...d_Harmful.html

BioPhysEngr, I agree that using "goto" is a bad practice. But why do modern languages, including C#, allow its usage? It is an unnecessary statement so it shouldn't be included in the language.

goto is useful when you want to jump out of nested loops. Used properly, it can make code clean. But its side effects outwin its usefulness.

Quote:

---

Originally Posted by Silent Sojourner

goto is useful when you want to jump out of nested loops. Used properly, it can make code clean. But its side effects outwin its usefulness.

---

I don't think I agree. I would always recommend against the use of goto. If I had to jump out of a nested loop I'd either:

(a) write a subroutine that could abort the loop using a return statement or
(b) use a bool that must be set to true to continue loop execution. The interior loop can set it to false to abort the loop and allow the loop to end naturally.

Quote:

---

Originally Posted by BioPhysEngr

I don't think I agree. I would always recommend against the use of goto. If I had to jump out of a nested loop I'd either:

(a) write a subroutine that could abort the loop using a return statement or
(b) use a bool that must be set to true to continue loop execution. The interior loop can set it to false to abort the loop and allow the loop to end naturally.

---

I know the goto label is bad. I'll remove it and add a subroutine but first I kind of want to work on the problem at hand before I do anything else.

Quote:

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Originally Posted by TheGreatCthulhu

First, remove "goto Start;" - no need for that at all.

Second, tell us:
(1) Is this an exception or a compiler error? If it's an exception, what is the type of the exception?
(2) What is the exact error message?
(3) At what line of that code it occurs?

Make sure you post the exact code you're currently using, the one that produces the error.

This line

while (guess != "Q");

could have caused it, but you've replaced it in the code sample you posted last.
As far as I can tell, if you copied the code you pasted here (from your last post) into VS, it would work just fine (except for the goto).

Could be that you forgot to change the type of one of your variables, or something. Read the error message carefully, double click it to be taken to the problematic line, see if there are any strings that are being used together with integers.

---

The code I'm using now is exactly the same as the last one I posted.

(1) The error is a compiler error.
(2) The exact error message is "Cannot implicitly convert type "string" to "int".
(3) Line 21, column 25. It's the "guess = Console.WriteLine();" line.

You have guess defined as an int, but Console.ReadLine() returns a string. That is the mismatch. That's why I gave you this line:
string guess_str = Console.ReadLine();
Then you can convert it to an integer using the statement:
guess_number = Convert.ToInt16(guess_str);
After you checked that the string is valid as a number, and not "Q".

Quote:

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Originally Posted by Krunchyman

The code I'm using now is exactly the same as the last one I posted.

(1) The error is a compiler error.
(2) The exact error message is "Cannot implicitly convert type "string" to "int".
(3) Line 21, column 25. It's the "guess = Console.WriteLine();" line.

---

Sorry for getting distracted with the goto discussion. The problem is as follows:

guess is declared as an int. Console.ReadLine() returns a string. You are trying to assign a variable of one type to a variable of a different type. In general, this is not allowed. You must first convert the string to an int. Do this like:

Code:

---

guess = Int32.Parse(Console.ReadLine());

---

Or even better

Code:

---

bool valid = false;
while( !valid )
{
    //Try to convert the string typed in to an integer and store it in guess
    //Valid will be assigned true only if this parsing succeeds.
    valid = Int32.TryParse(Console.ReadLine(), out guess);
}

---

The difference between Int32.Parse(string) and Int32.TryParse(string, out int) is that the former will convert the string to an int and throw an exception if given invalid input. The latter will convert a string to an int and give you a return value (bool) indicating whether or not the parsing was successful.

Quote:

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Originally Posted by Jim_Auricman

guess_number = Convert.ToInt16(guess_str);

---

Nitpick: This will convert guess_str to a short (which will then be automatically upcasted to an int). The preferred syntax when assigning an int is Convert.ToInt32(guess_str);. Actually, I like Int32.Parse(guess_str) most of all.

Aah, I missed that bit.

Look what u have:

Code:

---

01:        int guess;
02:        int.TryParse(Console.ReadLine(), out guess);
           
            //...

            // then later, in do-while:

03:                guess = Console.ReadLine();

---

Line 01 declares the guess to be an integer.

Line 02 is equivalent to:

string temp = Console.ReadLine();
int.TryParse(temp, out guess);

ReadLine returns a string, and try parse expects a string as its first parameter (this is the string you want to parse and convert to an integer). This is why, instead of the temp variable used here, you can put in the ReadLine() call directly - the method returns a string, and this result is passed as the parameter. Guess is passed by reference via the out keyword, which enables the TryParse() method to change the value of the variable internally, in a way that affects your original guess variable (that is, the method doesn't make it's own copy).
When TryParse() is done, guess will contain the appropriate value.

All that means that line 03 is completely redundant, aside from the fact that it won't compile. You can safely delete it. Again, the reason the compiler complains is because ReadLine() returns a string, but the guess variable now accepts only integers, as you yourself have declared in line 01.

Ok, so I finally got it to work, thanks to Jim's help. The code compiles without error and runs fine. Now, I just need to do some cleanup.

Here's the completed code. I added a statement where if you enter in "0", it exits the program and I also removed the goto statement. I also increased the number to 500,000, just to make things difficult for the unlucky user who decides to play this insane number game.

Code:

---

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("You must guess a number from 1 to 50000. If you guess the number correctly, you win.");
            int number;
            int guess;

            int.TryParse(Console.ReadLine(), out guess);
            Random rand;
            rand = new Random();

            number = rand.Next(1, 50000);
            do
            {
                string guess_str = Console.ReadLine();

                if (guess == number)
                {
                    Console.WriteLine("You've won.");
                }
                else
                {
                    Console.WriteLine("Sorry, guess again.");
                }
            } while (guess != number);
        }
    }
}

---

Thanks for everyone's help.