Errors and Exceptions Handling in C#

Errors and Exceptions Handling in C#

23 May 2024
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Errors and Exceptions: An Overview

Errors refer to the mistakes or faults that occur during program development or execution. If you don't find them and correct them, they cause a program to produce wrong results. In this C# Tutorial, we will explore more about Errors and Exceptions which will include exception handling in c#, types of errors in c#, try-catch-finally blocks in c#,and last proper use of try-catch, and finally block.

Types of Errors

In programming language errors can be divided into three categories as given below-

  1. Syntax Errors

    Syntax errors occur during development when you make type mistakes in code. For example, instead of writing while you write WHILE then it will be a syntax error since C# is a case-sensitive language.

     bool flag=true;
    
    WHILE (flag) //syntax error, since c# is case sensitive
    {
     //TO DO:
    }
    
  2. Runtime Errors (Exceptions)

    Runtime errors occur during the execution of the program. These are also called exceptions. This can be caused due to improper user inputs, improper design logic, or system errors.

     int a = 5, b = 0;
    int result = a / b; // DivideByZeroException
    
  3. Exceptions can be handled by using try-catch blocks.

  4. Logical Errors

    Logic errors occur when the program is written fine but does not produce the desired result. Logic errors are difficult to find because you need to know for sure that the result is wrong

     int a = 5, b = 6;
    double avg = a + b / 2.0; // logical error, it should be (a + b) / 2.0
    

Read More - C# Programming Interview Questions

Exception Handling

Exception handling is a mechanism to detect and handle run-time errors. It is achieved by using the Try-Catch-Finally blocks and throw keyword.

  1. Try block

    The try block encloses the statements that might throw an exception.

     try
    {
     // Statements that can cause exception.
    }
     
  2. Catch block

    Catch block handles any exception if one exists.

     catch(ExceptionType e)
    {
     // Statements to handle exception.
    }
    
  3. Finally block

    The finally block can be used for doing any clean-up process like releasing unused resources even if an exception is thrown. For example, disposing database connection.

     finally
    {
     // Statement to clean up.
    }
    
  4. Throw keyword

    This keyword is used to throw an exception explicitly.

     catch (Exception e)
    {
     throw (e);
    }  

Key points about exception handling

  1. Exceptions are types that all directly or indirectly derive from the System.Exception class.

  2. Exception objects contain detailed information about the error, such as the state of the call stack and a text description of the error.

  3. A try block is used to throw multiple exceptions that can be handled by using multiple catch blocks.

  4. A more specialized catch block should come before a generalized one. Otherwise specialized catch block will never be executed.

  5. Exceptions can be explicitly generated by a program by using the throw keyword.

  6. If no exception handling mechanism is used, the program stops executing with an error message.

  7. By providing a catch block without brackets or arguments, we can catch all exceptions that occur inside a try block.

     Catch
    {
     Console.WriteLine("oException" );
    } 
  8. By providing a catch block with an exception object, you can obtain more information about the type of exception that occurred.

     catch(Exception e)
    {
     Console.WriteLine(e.Message);
    }
    
  9. The statements inside the finally block are always executed whether an exception occurs or not in the program.

  10. Also, before the termination of the program finally block is always executed.

Order of Try-Catch-Finally blocks

In the order of exceptions handling, blocks try block comes first, after that catch block(s) comes, and the last finally block comes. Let's see in C# Compiler.

 try
{
 // statements that can cause exception.
}
catch (MoreSpecificExceptionType e1)
{
 // error handling code
}
catch (SpecificExceptionType e2)
{
 // error handling code
}
catch (GeneralExceptionType eN)
{
 // error handling code
}
finally
{
 // statement to clean up.
} 

You can also skip finally block if required.

 try
{
 // statements that can cause exception.
}
catch (MoreSpecificExceptionType e1)
{
 // error handling code
}
catch (SpecificExceptionType e2)
{
 // error handling code
}
catch (GeneralExceptionType eN)
{
 // error handling code
} 
  

You can also skip catch block(s) if required.

 try
{
 // statements that can cause exception.
}
finally
{
 // statement to clean up.
}

Hence a combination of try-catch-finally or try-catch or try-finally blocks is valid.

List of C# Exceptions :

List of C# Exceptions
Conclusion

I hope you will enjoy the exception handling in C# while programming. I would like to have feedback from my blog readers. Your valuable feedback, questions, or comments about this article are always welcome. Also, Consider our C# Programming Course for a better understanding of all C# concepts.

FAQs

Q1. What are the 4 keywords of exception handling in C#?

C# exception handling is built upon four keywords: try, catch, finally, and throw.

Q2. What is error and exception handling?

An error is an issue in a program that prevents the program from completing its task. In comparison, an exception is a condition that interrupts the normal flow of the program

Q3. How to throw exception with error code in C#?

Using the C# throw or the Visual Basic Throw statement. 

Q4. What is error in C#?

coding errors made by the programmer, errors due to wrong input, or other unforeseeable things

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About Author
Shailendra Chauhan (Microsoft MVP, Founder & CEO at Scholarhat by DotNetTricks)

Shailendra Chauhan is the Founder and CEO at ScholarHat by DotNetTricks which is a brand when it comes to e-Learning. He provides training and consultation over an array of technologies like Cloud, .NET, Angular, React, Node, Microservices, Containers and Mobile Apps development. He has been awarded Microsoft MVP 8th time in a row (2016-2023). He has changed many lives with his writings and unique training programs. He has a number of most sought-after books to his name which has helped job aspirants in cracking tough interviews with ease.
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