如何使用try / catch来检查数字是否在1-3的范围内？ C＃

Question

        /*Propmt user for beverages*/
        while (!bool_valid)
        {
            bool_valid = true;
            Console.WriteLine("Plesae Choose a Drink; Press 1 for Coke, Press 2 for Sprite, Press 3 for Dr.Prpper");
            try
            {
                int_bvg_type = Convert.ToInt32(Console.ReadLine());
                (int_bvg_type > 0) && (int_bvg_type < 4);
            }
            catch
            {
                Console.WriteLine("PLease enter a Number between 1 and 3");
                bool_valid = false;
            }
        }

I need to make sure a numerical input, as a variable, is between 1 and 3 and was wondering how to do it with C# and Try/Catch . I tried (int_bvg_type > 0) && (int_bvg_type < 4); ... but I get an error saying I cannot use it as a statement. Could someone please explain how to check to see if a number is between 1 and 3 using Try/Catch .

Answer 1

You need a simple if statement.Not try / catch

if(!(beverageType > 0 && beverageType < 4))
{
   Console.WriteLine("Please enter a Number between 1 and 3");
}

Or if you insist about using try/catch :

if(!(beverageType > 0 && beverageType < 4))
{
   throw new FormatException("Please enter a Number between 1 and 3");
}

And catch your FormatException :

catch(FormatException ex) 
{ 
    Console.WriteLine(ex.Message);
}

Answer 2

Try catch is not the recommended approach. Try catch is used for Exceptions. It will only work if your program actually raises an exception.

My recommended approach would be the following:

if(!(int_bvg_type > 0 && int_bvg_type < 4))
{
   Console.WriteLine("PLease enter a Number between 1 and 3");
}

If you still want to do it via try catch then this would do the trick. But frankly, it's just stupid code:

    /*Propmt user for beverages*/
    while (!bool_valid)
    {
        bool_valid = true;
        Console.WriteLine("Plesae Choose a Drink; Press 1 for Coke, Press 2 for Sprite, Press 3 for Dr.Prpper");
        try
        {
            int_bvg_type = Convert.ToInt32(Console.ReadLine());
            if(!(int_bvg_type > 0 && int_bvg_type < 4)){
                throw new Exception();
            }
        }
        catch
        {
            Console.WriteLine("PLease enter a Number between 1 and 3");
            bool_valid = false;
        }
    }

Answer 3

You don't need a try/catch statement.

bool validInput = false;

while (!validInput)
{
    Console.WriteLine("Please choose a Drink; Press 1 for Coke, Press 2 for Sprite, Press 3 for Dr.Prpper");

    int_bvg_type = int.Parse(Console.ReadLine());

    if ((int_bvg_type > 0) && (int_bvg_type < 4))
        validInput = true;
}

You could also look into int.TryParse if someone might enter a non-numeric character.

Answer 4

Can i recommend the following as good structure:

while(true){
    try{
        Console.WriteLine("Please Choose a Drink; Press 1 for Coke, Press 2 for Sprite, Press 3 for Dr.Prpper");
        switch(int.Parse(Console.ReadLine())){
            case 1:
                //do coke
                break;
            case 2:
                //do sprite
                break;
            case 3:
                //do dr pepper
                break;
            default:
                //your message is shown if no matching rules were found, not based on a secondry range check
                Console.WriteLine("Im not sure what to do with that option");
                break;    
        }
    }
    //be explicit about the exceptions you want to catch
    catch(FormatException){
        Console.WriteLine("What you entered wasnt a number");
    }
}

Answer 5

(int_bvg_type > 0) && (int_bvg_type < 4);

Your line is an expression, and it needs to be assigned to a variable, or evaluated, like in an if statement.

The try catch is not something you will need, as everyone has said, just use an if statement.