Question

I was just wondering about some CodeWarning (ConstructorsShouldNotCallBaseClassVirtualMethods), and if there is a better way to do it. I have a simple log collector class, and I am using NHibernate to retrieve some of the objects.

Some times I create objects by myself (of course) and add them to NHibernate for persistance. What is the best way to make sure that Lists are never NULL.

Currently I am doing this, but it does not seems “perfect”. Any idea on this topic?

public class LogRun
{
    public virtual int Id { get; private set; }
    public virtual DateTime StartTime { get; set; }
    public virtual DateTime EndTime { get; set; }
    public virtual IList<Log> LogMessages { get; set; }
    public virtual int LogMessageCount { get { return LogMessages.Count; } }

    public LogRun()
    {
        LogMessages = new List<Log>();
    }


}

Answer 1

Is LogMessages a persisted thing? If so, it’s best practice to never expose a public setter. NHibernate gets weird if you retreive from the database and then replace that IList with a new one:

var myLog = session.Get<LogRun>(1);
Assert.True(myLog.LogMessages.Count > 0);
myLog.LogMessages = new List<Log>();

If you note, NHibernate is returning a proxied object and replacing it with a generic list will cause it to go wonky when you try and save back.

As a rule, I prefer to have a private field that I initialize and then expose only a getter to the client:

public class LogRun
{
    private IList<Log> logMessages = new List<Log>();

    public virtual int Id { get; private set; } 
    public virtual DateTime StartTime { get; set; } 
    public virtual DateTime EndTime { get; set; }
    public virtual IList<Log> LogMessages { get { return logMessages; } } 
    public virtual int LogMessageCount { get { return LogMessages.Count; } }

    public void AddLogMessage(Log log)
    {
        logMessages.Add(log);
    }
}

Actually, I go a step further, the client gets an IEnumerable<> and I add a helper function for the add.

My implmentation would look like

public class LogRun
{
    private IList<Log> logMessages = new List<Log>();

    public virtual int Id { get; private set; } 
    public virtual DateTime StartTime { get; set; } 
    public virtual DateTime EndTime { get; set; }
    public virtual IEnumerable<Log> LogMessages { get { return logMessages; } } 
    public virtual int LogMessageCount { get { return LogMessages.Count(); } }

    public void AddLogMessage(Log log)
    {
        logMessages.Add(log);
    }
}