How to warn user if he/she inputs "string" instead of "integer" in C# console?

Question

Here is my simple and newbie program written in C#. I have just tried it for integers but when I tried to input naturally it throws an execption. I wonder how to warn user if any string input occurs without throwing the exception. ( PS: I am an absoulute beginner).

float quiz, mid, final,avg;
Console.WriteLine("Enter quiz score:");
quiz= float.Parse(Console.ReadLine());
Console.WriteLine("Enter mid-term score:");
mid = float.Parse(Console.ReadLine());
Console.WriteLine("Enter final score:");
final = float.Parse(Console.ReadLine());

avg=(quiz+mid+final)/3;

while (avg<=100 && quiz<=100&& mid <=100 && final<=100 )
{

    if (avg >= 90)
        Console.WriteLine("Grade A");

    else if (avg >= 70 && avg < 90)
        Console.WriteLine("Grade B");

    else if (avg >= 50 && avg < 70)
        Console.WriteLine("Grade C");

    else if (avg < 50)
        Console.WriteLine("Grade F");
    else
        Console.Write("invalid operation!!");
    break;
}
while (avg > 100)
{
    Console.WriteLine("Please enter the right scores!");
    //Console.ReadLine();
    break;
}
while (mid > 100)
{
    Console.WriteLine("Please enter the right scores!");
    //Console.ReadLine();
    break;
}
while (final > 100)
{
    Console.WriteLine("Please enter the right scores!");
    //Console.ReadLine();
    break;
}

while (quiz > 100)
{
    Console.WriteLine("Please enter the right scores!");
    //Console.ReadLine();
    break;
}
Console.ReadLine();

Actually there must not be any string input according to flow logic.I unsurely think that there is nothing to convert from string into integers OR I prolly do not understand what you mean. Could you explain it? :) — SophisticatedUndoing
– SophisticatedUndoing, Commented Jun 29, 2015 at 13:12

malhotraprateek · Accepted Answer · 2015-06-29 12:21:50Z

1

You could try this:

bool isNumeric;
int i = -1;
string str = Console.ReadLine();

isNumeric = int.TryParse(str, out i);
if(isNumeric == false)
    Console.WriteLine("Not an integer");

Taken from here

answered Jun 29, 2015 at 12:21

malhotraprateek

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Comments

SophisticatedUndoing · Accepted Answer · 2015-06-29 14:23:38Z

I have just implemented the "isNumeric" solution and encountered a problem with integer definition cuz I use float type variables. I re-arranged and modified my codes. Here is the last working version :

bool isNumeric;
        float i;
        string str;
        string name = "";
        float quiz=0;
        float mid=0;
        float final=0;
        float avg=0;


        Console.WriteLine("Please enter your name:");
        name = Console.ReadLine();

        while (true)
        {
            Console.WriteLine("Enter quiz score:");



            str = Console.ReadLine();
            isNumeric = float.TryParse(str, out i);



            if (isNumeric)
            {

                quiz = float.Parse(str);
                if (quiz>100)
                {
                    Console.WriteLine("Please enter the right scores!");
                }
                else
                {
                    break;
                }

            }
            else
            {

                Console.WriteLine("Not an integer");


            }

        }

        while (true)
        {
            Console.WriteLine("Enter mid-term score:");
            str = Console.ReadLine();
            isNumeric = float.TryParse(str, out i);
            if (isNumeric == false)
            {
                Console.WriteLine("Not an integer");
            }
            else
            {
                mid = float.Parse(str);
                if(mid>100)
                {
                    Console.WriteLine("please input the right score");
                }
                else
                {
                    break;
                    }


            }
        }

        while (true)
        {
            Console.WriteLine("Enter final score:");
            str = Console.ReadLine();
            isNumeric = float.TryParse(str, out i);
            if (isNumeric == false)
            {
                Console.WriteLine("Not an integer");
            }
            else
            {
                final = float.Parse(str);
                if (final > 100)
                {
                    Console.WriteLine("Please enter the right scores!");
                }
                else
                {
                    break;
                }
            }
        }

        avg = (quiz + mid + final) / 3;

        while (avg <= 100 && quiz <= 100 && mid <= 100 && final <= 100)
        {

            if (avg >= 90)
                Console.WriteLine(name+" 's Grade is A");

            else if (avg >= 70 && avg < 90)
                Console.WriteLine(name+ " 's Grade is B");

            else if (avg >= 50 && avg < 70)
                Console.WriteLine(name+ "Grade C");

            else if (avg < 50)
                Console.WriteLine("Grade F");
            else
                Console.Write("invalid operation!!");
            break;
        }


        Console.ReadLine();

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