Error handling in C#

Exception handling in C#, suppoted by the try catch and finaly block is a mechanism to detect and handle run-time errors in code. The .NET framework provides built-in classes for common exceptions. The exceptions are anomalies that occur during the execution of a program. They can be because of user, logic or system errors. If a user (programmer) does not provide a mechanism to handle these anomalies, the .NET runtime environment provide a default mechanism, which terminates the program execution.

C# provides three keywords try, catch and finally to implement exception handling. The try encloses the statements that might throw an exception whereas catch handles an exception if one exists. The finally can be used for any cleanup work that needs to be done.

ry..catch..finally block example:

try
{
// Statement which can cause an exception.
}
catch(Type x)
{
// Statements for handling the exception
}
finally
{
//Any cleanup code
}

Following are some common exception classes:

Exception Class - - Cause
SystemException - A failed run-time check;used as a base class for other.
AccessException - Failure to access a type member, such as a method or field.
ArgumentException - An argument to a method was invalid.
ArgumentNullException - A null argument was passed to a method that doesn't accept it.
ArgumentOutOfRangeException - Argument value is out of range.
ArithmeticException - Arithmetic over - or underflow has occurred.
ArrayTypeMismatchException - Attempt to store the wrong type of object in an array.
BadImageFormatException - Image is in the wrong format.
CoreException - Base class for exceptions thrown by the runtime.
DivideByZeroException - An attempt was made to divide by zero.
FormatException - The format of an argument is wrong.
IndexOutOfRangeException - An array index is out of bounds.
InvalidCastExpression - An attempt was made to cast to an invalid class.
InvalidOperationException - A method was called at an invalid time.
MissingMemberException - An invalid version of a DLL was accessed.
NotFiniteNumberException - A number is not valid.
NotSupportedException - Indicates sthat a method is not implemented by a class.
NullReferenceException - Attempt to use an unassigned reference.
OutOfMemoryException - Not enough memory to continue execution.
StackOverflowException - A stack has overflown.

An exception is a problem that arises during the execution of a program. A C# exception is a response to an exceptional circumstance that arises while a program is running, such as an attempt to divide by zero.

Exceptions provide a way to transfer control from one part of a program to another. C# exception handling is built upon four keywords: try, catch, finally, and throw.

• try − A try block identifies a block of code for which particular exceptions is activated. It is followed by one or more catch blocks.

• catch − A program catches an exception with an exception handler at the place in a program where you want to handle the problem. The catch keyword indicates the catching of an exception.

• finally − The finally block is used to execute a given set of statements, whether an exception is thrown or not thrown. For example, if you open a file, it must be closed whether an exception is raised or not.

• throw − A program throws an exception when a problem shows up. This is done using a throw keyword.

Syntax

Assuming a block raises an exception, a method catches an exception using a combination of the try and catch keywords. A try/catch block is placed around the code that might generate an exception. Code within a try/catch block is referred to as protected code, and the syntax for using try/catch looks like the following 

try {
   // statements causing exception
} catch( ExceptionName e1 ) {
   // error handling code
} catch( ExceptionName e2 ) {
   // error handling code
} catch( ExceptionName eN ) {
   // error handling code
} finally {
   // statements to be executed
}

You can list down multiple catch statements to catch different type of exceptions in case your try block raises more than one exception in different situations.

Exception Classes in C#

C# exceptions are represented by classes. The exception classes in C# are mainly directly or indirectly derived from the System.Exception class. Some of the exception classes derived from the System.Exception class are the System.ApplicationException and System.SystemException classes.

The System.ApplicationException class supports exceptions generated by application programs. Hence the exceptions defined by the programmers should derive from this class.

The System.SystemException class is the base class for all predefined system exception.

The following table provides some of the predefined exception classes derived from the Sytem.SystemException class

Handling Exceptions

C# provides a structured solution to the exception handling in the form of try and catch blocks. Using these blocks the core program statements are separated from the error-handling statements.

These error handling blocks are implemented using the try, catch, and finally keywords. Following is an example of throwing an exception when dividing by zero condition occurs

using System;

namespace ErrorHandlingApplication {
   class DivNumbers {
      int result;
      
      DivNumbers() {
         result = 0;
      }
      public void division(int num1, int num2) {
         try {
            result = num1 / num2;
         } catch (DivideByZeroException e) {
            Console.WriteLine("Exception caught: {0}", e);
         } finally {
            Console.WriteLine("Result: {0}", result);
         }
      }
      static void Main(string[] args) {
         DivNumbers d = new DivNumbers();
         d.division(25, 0);
         Console.ReadKey();
      }
   }
}

When the above code is compiled and executed, it produces the following result

Exception caught: System.DivideByZeroException: Attempted to divide by zero. 
at ...
Result: 0

Creating User-Defined Exceptions

You can also define your own exception. User-defined exception classes are derived from the Exception class. The following example demonstrates this

using System;

namespace UserDefinedException {
   class TestTemperature {
      static void Main(string[] args) {
         Temperature temp = new Temperature();
         try {
            temp.showTemp();
         } catch(TempIsZeroException e) {
            Console.WriteLine("TempIsZeroException: {0}", e.Message);
         }
         Console.ReadKey();
      }
   }
}
public class TempIsZeroException: Exception {
   public TempIsZeroException(string message): base(message) {
   }
}
public class Temperature {
   int temperature = 0;
   
   public void showTemp() {
      
      if(temperature == 0) {
         throw (new TempIsZeroException("Zero Temperature found"));
      } else {
         Console.WriteLine("Temperature: {0}", temperature);
      }
   }
}

When the above code is compiled and executed, it produces the following result

TempIsZeroException: Zero Temperature found

Throwing Objects

You can throw an object if it is either directly or indirectly derived from the System.Exception class. You can use a throw statement in the catch block to throw the present object as 

Catch(Exception e) {
   ...
   Throw e
}

I have implemented elegant error handling in my project :

TuralSuleymani/CTeleportAssignment (github.com)

https://www.geeksforgeeks.org/exception-handling-in-c-sharp/
https://www.tutorialspoint.com/csharp/csharp_exception_handling.htm

An error/exception is a problem that arises during the execution of a program. A C# exception is a response to an exceptional circumstance that arises while a program is running.

Exceptions provide a way to transfer control from one part of a program to another. C# exception handling is built upon four keywords: try, catch, finally, and throw.

C# exceptions are represented by classes. The exception classes in C# are mainly directly or indirectly derived from the System.Exception class. See below graphical representation to understand sub categories:

Reference: https://www.tutorialsteacher.com/csharp/csharp-exception

Please check the below links.
https://www.c-sharpcorner.com/article/exception-handling-in-C-Sharp/
https://www.geeksforgeeks.org/exception-handling-in-c-sharp/
https://www.tutorialspoint.com/csharp/csharp_exception_handling.htm