Logging user-defined exception C#

Question

Hello I would like to write my userdefined exception to a log file. So Instead of throwing my exception I would like to log that message into a txt file.

The constructor for my exception looks like this:

public OpenFileException(string pathToOpen, Exception innerexception)
    : base("Couldn't find the path: " + pathToOpen, innerexception)
{
    this.pathToOpen = pathToOpen;
}

This is how I am logging my exception at the moment:

try
{
    string data = Read(txtLocation.Text);
    txtInfo.Text = data;

}
catch (Exception ex)
{

    WriteLog("[" + DateTime.Now + "]" + " " + ex.Message);
    MessageBox.Show(" ");       
    throw new OpenFileException(txtLocation.Text, ex);                
}

So what I'm asking is. How can I log my string "Couldn't find the path: " to a txt file?

Answer 1

I would normally catch and log the user defined exception outside the normal try/catch

try {
    try {
        string data = Read(txtLocation.Text);
        txtInfo.Text = data;
    } catch (Exception ex) {
        throw new OpenFileException(txtLocation.Text, ex);
    }

        ....

} catch(OpenFileException ex) { 
    WriteLog("[" + DateTime.Now + "]" + " " + ex.Message);
    MessageBox.Show(" ");   
} catch(Exception ex) { 
    WriteLog("[" + DateTime.Now + "]" + " " + ex.Message);
    MessageBox.Show(" ");   
}

You are creating a user defined exception so you can handle it differently

Answer 2

It looks a bit overkilling, why don't you use Log4Net and let it write files or send you emails depending on its configuration in the app.config?

basically you get all what you can want out of the box with no effort, then you can concentrate on what matters the most.

even if you decide to keep your current logic, I would anyway create a Logger class which does everything instead of having to specify DateTime.Now and other magic in every single catch block of your application.

Answer 3

You can use, instead of reinvent the wheel, log4net http://logging.apache.org/log4net/ or NLog http://nlog-project.org/wiki/Documentation both worth the effort to learn and use even in simple applications.

Answer 4

You need to find a way to get your exception thrown when a file is not found.

I don't think this is a good idea, because .NET already throws the FileNotFoundException when a file is not found. You should catch that and log the message that way.

try
{
    string data = Read(txtLocation.Text);
    txtInfo.Text = data;

}
catch (FileNotFoundException ex)
{
    string log = String.Format("[{0}] Couldn't find the path: {1}"
                              , DateTime.Now
                              , ex.FileName);
    WriteLog(log);
}

Don't make a new exception type when one already exists.

(Forgive the idiosyncrasies in my formatting)

Answer 5

From Framework Desing Guidelines:

Do override ToString when your exception provides extra properties.

Then you can just call log.Error(exception) and it will be logged just the way you wrote ToString() without extra actions.