通过Try-Catch块C＃进行验证

Question

I am a beginner at C# and I am trying to use a 'Try and catch' block to act as a validation when the user inputs something. It works when the user enters an invalid input the first time but the system crashes when the user enters an invalid input the second time.

I tried to get through this problem by creating a bool variable which is set true until user inputs correct input but have not been very successful.

The main problem is I don't know how to make the system set the bool variable to false when the user inputs a correct input

C# Code:

while (invalidInput == true)
{
    try
    {
        {
            Console.Write("Landscape Size: ");
            LandscapeSize = Convert.ToInt32(Console.ReadLine());
            Console.Write("Initial number of warrens: ");
            InitialWarrenCount = Convert.ToInt32(Console.ReadLine());
            Console.Write("Initial number of foxes: ");
            InitialFoxCount = Convert.ToInt32(Console.ReadLine());
            Console.Write("Randomness variability (percent): ");
            Variability = Convert.ToInt32(Console.ReadLine());
            FixedInitialLocations = false;
        }
        Sim = new Simulation(LandscapeSize, InitialWarrenCount, InitialFoxCount, Variability, FixedInitialLocations);
    }
    catch
    {
        Console.WriteLine("invalid input!");
        LandscapeSize = Convert.ToInt32(Console.ReadLine());
        InitialWarrenCount = Convert.ToInt32(Console.ReadLine());
        InitialFoxCount = Convert.ToInt32(Console.ReadLine());
        Variability = Convert.ToInt32(Console.ReadLine());
        invalidInput = true;
    }
    invalidInput = false;
}

Also, I am new to stack overflow so sorry if I make any mistakes.

So my question is what am I doing wrong? Thank you

Answer 1

The problem your having is that invalidInput is set to false every time the loop is executed - independent of the try-catch block. Move it to the end of the try-block instead, this way you will ensure that all the code in the try-block does not throw an error before you set the flag. However, since exceptions rarely are used for control-flow you should probably use some kind of control-statement like an if-statement .

Answer 2

You only need to set invalidInput to false at the end of the try block .

However, use int.TryParse to control flow instead of exceptions.

int landscapeSize;

Console.Write("Landscape Size: ");
while(!int.TryParse(Console.ReadLine(), out landscapeSize))
{
    Console.Write("Invalid input. Enter landscape size: ");
}

Do this for all your inputs.