Where is my mistake? (Do-while loop)

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Hi guys, (i'm a beginner :) i defined a variable (string = userSecondInput) in the do-while loop ("do" part), but i can't use the variable in the "while"! why? :(
please help me :( i'm

What I have tried:

Console.WriteLine("Please Enter Your name: ");
string userInput = Console.ReadLine();
if (string.IsNullOrEmpty(userInput))
{
    do
    {
        Console.WriteLine("invalid value! Please Enter Your name: ");
        string userSecondInput = Console.ReadLine();
    } while (userSecondInput == "");
}
Console.WriteLine("welcome " + userInput);
Console.ReadKey();

Posted 16-Feb-17 22:41pm

Amir Hossein Hmd

Updated 16-Feb-17 23:37pm

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Patrice T 17-Feb-17 4:47am

Define: 'but i can't use the variable in the "while"!'
What is the problem.

3 solutions

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F-ES Sitecore · Answer 1 · 2017-02-16T22:48:00

This is called "scope". When you define a variable inside a section of curly brackets ({ ... }) then it isn't visible outside of those brackets.

do
{
    Console.WriteLine("invalid value! Please Enter Your name: ");
    string userSecondInput = Console.ReadLine(); // defined here
} while (userSecondInput == ""); //can't be seen here as outside of the brackets it is defined in

Do something like

Console.WriteLine("Please Enter Your name: ");
string userInput = Console.ReadLine();
string userSecondInput = null;
if (string.IsNullOrEmpty(userInput))
{
    do
    {
        Console.WriteLine("invalid value! Please Enter Your name: ");
        userSecondInput = Console.ReadLine();
    } while (userSecondInput == "");
}

Karthik_Mahalingam · Answer 2 · 2017-02-16T22:51:00

No need to create a variable inside the loop, you shall use the existing one.

static void Main(string[] args)
        {
            Console.WriteLine("Please Enter Your name: ");
            string userInput = Console.ReadLine();
            if (string.IsNullOrEmpty(userInput))
            {
                do
                {
                    Console.WriteLine("invalid value! Please Enter Your name: ");
                      userInput = Console.ReadLine();
                } while (userInput == "");
            }
            Console.WriteLine("welcome " + userInput);
            Console.ReadKey();
        }

Peter Leow · Answer 3 · 2017-02-16T22:56:00

You have to create a variable before the loop if you want to use it in a loop condition. But why do you need

userSecondInput

, it has never been used outside of the loop. You just want to capture none-empty input from the user, just use

userInput

will do. Try this

		if (string.IsNullOrEmpty(userInput))
{
    do
    {
	 Console.WriteLine("invalid value! Please Enter Your name: ");
	 userInput = Console.ReadLine();
    }
    while (string.IsNullOrEmpty(userInput));
}

Where is my mistake? (Do-while loop)

3 solutions

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