Where to put try catch

Question

0.00/5 (No votes)

See more:

Hi,

I have been working on a project with layered architecture. I am confused at a stage where to catch and where to throw exception. here is the scenario

presentation layer:

C#

protected void btnLogin_Click(object sender, EventArgs e)
        {
            try
            {
                userName = txtUserName.Text;
                passWord = txtPassword.Text;
                dtLoginDetail = UserDetail.Login(userName, passWord);
                if (dtLoginDetail.Rows.Count > 0)
                {
                    returnUrl = "~/AuthenticatedUsers/Home.aspx";
                    Response.Redirect(returnUrl, false);
                }
                else
                {
                    lblLoginMessage.Text = "Invalid Username or Password!";
                    error = true;
                }
            }
            catch (NullReferenceException rx)
            {
                lblLoginMessage.Text = "Error connecting to server! Please check your internet connection";
                error = true;
            }
            catch (MySqlException mx)
            {
                lblLoginMessage.Text = "Sorry, Failed to Login. Please try after some time.";
                error = true;
            }
            if (error)
            {
                //show error
            }
      }

business layer:

C#

public DataTable Login(string username, string password)
{
    DataTable dtLoginDetails = new DataTable();
    Login loginAction = new Login();
    dtLoginDetails = loginAction.ValidateUser(username, password);
    return dtLoginDetails;
}

Data Layer:

C#

public DataTable ValidateUser(string username, string password)
{
    DataTable dtLoginDetails = new DataTable();

    try
    {
        string selectQuery = "SELECT user_id FROM user_details WHERE username='" + username + "' AND password='" + password + "' LIMIT 1";
        dtLoginDetails = connection.SelectCommand(selectQuery);
        return dtLoginDetails;
    }
    catch (NullReferenceException rx)
    {
        throw;
    }
    catch (MySqlException mx)
    {
        throw;
    }
}

Please let me know what is the best practice in giving the try catch in layer? should i throw specific error as i did in the baove code?

Thanks,
Amrutha

Posted 8-Jun-14 23:49pm

AmruthaNair

Updated 8-Jun-14 23:51pm

CPallini

v2

Add a Solution

3 solutions

Solution 2

Hi Friend,

you can make code with try catch whenever you have possibility to error occur(any Layer).
if you want to display error Message then write "throw ex" from Sub Layer(Business layer,Data Layer).
And Display this Error Message From presentation layer in Catch Block Using ex.Message.

Posted 9-Jun-14 0:13am

Nayan Rudani

Updated 9-Jun-14 0:15am

v2

Solution 1

Read this.. :)

try-catch (C# Reference)[^]

C# Catch[^]

Try ... Catch in C# .NET[^]

Lesson 15: Introduction to Exception Handling[^]

C# - Exception Handling[^]

A Deep Dive into C# Errors or Exceptions Handling[^]

Try-Catch-Finally in C#[^]

Why are braces required in try-catch-finally?[^]

Posted 9-Jun-14 0:11am

Nirav Prabtani

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

*Suvabrata Roy* · Accepted Answer · 2014-06-09T00:21:00

Hi Amrutha,

Its not a good practice to re-throw an error so please avoid it.

What you required to do when a error occurred there are several ways to handle it but you should know whats the actual requirement is.
In your case I think enum will do the trick.

Create a enum

C#

public enum ErrorTypes
{
NoError=0,
SQL=1,// SQL related 
Logical=2,//Business logic
Data=4, // Database related 
ErrorUndefine=8
// So on as you need 
}
// function signature for Business and Data Layer: add a out parameter 

public bool LogIn ([Your parameters],out ErrorTypes Error);

Now put try catch block in Business and Data Layer Like

C#

try {
}catch(Exception ex)
{
Error=ErrorUtil.SetErrorType(ex);
}
// The function 

public class ErrorUtil
{
public static ErrorTypes SetErrorType(Exception ex)
{
  if(ex is SQLException)
    {
      return ErrorTypes.SQL;
    }
// So on 
}
}
// After call of Business or Data layer just check what kind of error its returning.

But always remember that its better to check validity of data rather that waiting for a run time error.

Thanks
Suvabrata