Creating custom exceptions

Creating custom exceptions

Exceptions are very use full while developing high level applications; normally we are using the try catch block to catch the exceptions thrown by the .net frame work. As the same way we can create/handle our own exceptions.

Rule: All types of exceptions must derive from “System.Exception" class.

Here's the simple example. I have created a exception class named “InvalidUserException" which I am invoking when the current user is not valid to access the application.

//Creating own exception by inheriting the Exception class
public class InvalidUserException:Exception
{
    public override string Message
    {
        get
        {
            return "Invalid User";
        }
    }
}								
public class LoginManager
{
    //Instead of hard coded values you can add logic to retrive from the database
    public string ValidUserName="Admin";
    public string ValidPassword="AdminPass";
    
    public bool ValidateUser(string userName,string password)
    {
        if (ValidUserName == userName && ValidPassword == password)
        {
            //Login successful
            return true;
        }
        {
            //Login Failed
            throw new InvalidUserException();
        }
    }
}								



public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

   

    private void Form1_Load(object sender, EventArgs e)
    {
        LoginManager lm = new LoginManager();

        string currentLoginName = textBox1.Text;
        string currentLoginPassword = textBox2.Text;
        try
        {
            if (lm.ValidateUser(currentLoginName, currentLoginPassword))
            {
                //User is valid,Open next form
                MessageBox.Show("Login Success");
            }
        }
            //Catching the custom exception
        catch (InvalidUserException ex)
        {
            MessageBox.Show(ex.Message, "Login Faild", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
            
            //Resets the input elements
            textBox1.Text = string.Empty;
            textBox2.Text = string.Empty;
        }
        

    }

    
}