Question

I have a web app that contains an activity log for actions the users take. There are multiple types of activities that can be logged.

Here’s an example:

public static class NewAccountActivity() {
  public static Write(string username) {
    //... do stuff to enter a new account activity into the database ...
  }
}
public static class NewPostActivity() {
  public static Write(string username, long postId, string postTitle) {
    //... do stuff to enter a new post activity entry into the database ...
  }
}

And then go on to create a new class for every single type of activity to log. Each activity has a .Write() method, with a unique signature for each one (as shown in the code example above)

And then in my web app (asp.net mvc based) I use them like this:

public ActionResult NewAccount(Account account) {
  if (Model.IsValid(account)) {
    //... do new account stuff ...

    NewAccountActivity.Write(account.UserName);

    //... redirect to action, or show view ...
  }
}

public ActionResult NewPost(Post post) {
  if (Model.IsValid(post)) {
    //... do new post stuff ...

    NewPostActivity.Write(post.UserName, post.postId, post.Title);

    //... redirect to action, or show view ...
  }
}

Is this a bad idea? Is there a better way? Should these be a bunch of methods jammed into one class?

I started doing this because of an answer to a different question I had on SO.

Answer 1

This is my suggestion.

First of all, no static class should represent an activity. The Logger class can be static, or accessible through a DI container.

Create an interface for an activity, namely IActivity that has a single Write or Log method. For each activity where the processing is bigger than a single line of code, create a class that implements the IActivity interface.

Now for all other simple activity log, create a default activity that accept a function lambda.

Example, in this code, I assume that each activity builds a string and return it through the Log function:

public class NewAccountActivity : IActivity
{
    private string userName;

    public NewAccountActivity(string userName)
    {
        this.userName = userName;
    }

    public string Log()
    {
        return this.UserName;
    }
}

public class ActivityEntry : IActivity
{
    private Func<string> action;

    public ActivityEntry(Func<string> action)
    {
        this.action = action;
    }

    public string Log()
    {
        return this.action();
    }
}

Now in your static Logger class, create two functions:

public static class Logger
{
    public static void Write(IActivity activity)
    {
        // Ask activity for its data and write it down to a log file
        WriteToFile(activity.Log());
    }

    public static void Write(Func<string> action)
    {
        Write(new ActivityEntry(action));
    }
}

Then in your code, call your logger class like this:

Logger.Write(new NewAccountActivity(currentUserName));

or if you need to log something else that is simple:

Logger.Write(() => "Hello world");

This last call will create a new instance of ActivityEntry that will log “Hello World”.