Variable Scope in C#

Question

My web service program is supposed to generate a random code and return it to the client program. Right now it returns "" as the code instead of the randomly generated code. What is wrong with my variable scopes? Thanks.

public class Service1 : System.Web.Services.WebService
{
    private string code = "";

    [WebMethod]
    public void StartGame()
    {
        // Pick a secret code
        // R, B, G, O, T, W, P, Y
        Random random = new Random();
        for (int i = 0; i < 4; i++)
        {
            int num = random.Next(8) + 1;
            if (num == 1)
                this.code += "R";
            else if (num == 2)
                this.code += "B";
            else if (num == 3)
                this.code += "G";
            else if (num == 4)
                this.code += "O";
            else if (num == 5)
                this.code += "T";
            else if (num == 6)
                this.code += "W";
            else if (num == 7)
                code += "P";
            else if (num == 8)
                this.code += "Y";
        }
    }

    [WebMethod]
    public string MakeGuess(string guess)
    {
        return this.code;
    }
}

Answer 1

The problem is those methods get called on two separate instances of the class. Each method is invoked once on a new instance of the class as an HTTP request comes in and the class will be thrown away. The server will have no idea that those requests are related in some way due to the stateless nature of HTTP protocol.

Answer 2

Are you making two different calls , one to invoke the start game and another to call the MakeGuess? separate calls would imply creation of different objects on the server side. You should create sessions or make the code var static.

Answer 3

If there is no specific need for two calls why not making a simple method?

`

[WebMethod]
    public string MakeGuess(string guess)
    {
        private string code = "";
        // Pick a secret code
        // R, B, G, O, T, W, P, Y
        Random random = new Random();
        for (int i = 0; i < 4; i++)
        {
            int num = random.Next(8) + 1;
            if (num == 1)
                this.code += "R";
            else if (num == 2)
                this.code += "B";
            else if (num == 3)
                this.code += "G";
            else if (num == 4)
                this.code += "O";
            else if (num == 5)
                this.code += "T";
            else if (num == 6)
                this.code += "W";
            else if (num == 7)
                code += "P";
            else if (num == 8)
                this.code += "Y";
        }
        return code;
    }

Answer 4

Presented without additional comment:

public static string GenerateRandomCode(int length)
{
    const string charset = "RBGOTWPY";

    string randomCode = "";
    Random random = new Random();

    while (length > 0)
    {
        length--;
        randomCode += charset[random.Next(charset.Length)];
    }
    return randomCode;
}