Exception handling

Exception is defined as an event that occurs during the execution of a program that is unexpected by the program code. The actions to be performed in case of occurrence of an exception is not known to the program. In such a case, we create an exception object and call the exception handler code. The execution of an exception handler so that the program code does not crash is called Exception handling. Exception handling is important because it gracefully handles an unwanted event, an exception so that the program code still makes sense to the user.

We already studied what is Run time error, In simple terms Exception handling is something which is used to hangle the run time errors. Because if there is any compile time error system will not even compile the code whereas programmer don't have any control over run time errors because run time error is caused due to improper user inputs.

Try executing code example what we've given while we studied Run time error. If you compile that code it will crash your console application and start showing exception in your visual studio. If we want to protect our application from crashing we need to use Exception Handling. We'll see about exception handling using code in detail below

Syntax
try {
    // Code we need to try
}
catch {
    // Instruct system what it need to do it catches any run time error
}

CODE

EG 1 . Getting number from user

static void Main(string[] args) {
    try {
        Console.Write("Enter Number : ");
        int num = Convert.ToInt32(Console.ReadLine());
    }
    catch {
        Console.WriteLine("Invalid Entry");
    }
}

CODE EXPLANATION
Try compiling the above code, give some alphabets as input. System won't crash console instead it will show "Invalid Entry" text. So what happening here is, System enters try and execute whatever the code we written inside if it catches any run time error it will jump to catch and execute whatever the code we written inside. In case inside try if system doesn't catch any run time error, system will skip whatever code we written inside catch.


EG 2 . Getting number from user printing exact Exception thrown by system

static void Main(string[] args) {
    try {
        Console.Write("Enter Number : ");
        int num = Convert.ToInt32(Console.ReadLine());
    }
    catch (Exception e){
        Console.WriteLine(e.Message);
    }
}

CODE EXPLANATION
Inside ( ) of catch we used a class called Exception. The use of that Exception is to store the Exception message thrown by the system. Now print the message stored inside e. Try compiling the program by giving some alphabets as input. If you follow all above steps system will print out message stating "Input string was not in a correct format." which is the exact Exception message thrown by the system.


Exercises
1. Get Multiplication table and Limit value from user and print that multiplication table from 1 to entered limit. Use exception handling for the case where user enter any non integer number or alphabets.
2. Get A and B value from user and find A / B. Use exception handling for the case where user enter 0 for B.


(Click Here, For more exercises)