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5 Steps for Coding for the Next Developer

Most of us probably don’t think about the developer who will maintain our code. Until recently, I did not consider him either. I never intentionally wrote obtuse code, but I also never left any breadcrumbs.

Kent Beck on good programmers:

Any fool can write code that a computer can understand. Good programmers write code that humans can understand.

Douglas Crockford on good computer programs:

It all comes down to communication and the structures that you use in order to facilitate that communication. Human language and computer languages work very differently in many ways, but ultimately I judge a good computer program by it’s ability to communicate with a human who reads that program. So at that level, they’re not that different.

Discovering purpose and intent is difficult in the most well written code. Any breadcrumbs left by the author, comments, verbose naming and consistency, is immensely helpful to next developers.

I start by looking for patterns. Patterns can be found in many places including variables names, class layout and project structure. Once identified, patterns are insights into the previous developer’s intent and help in comprehending the code.

What is a pattern? A pattern is a repeatable solution to a recurring problem. Consider a door. When a space must allow people to enter and to leave and yet maintain isolation, the door pattern is implemented. Now this seems obvious, but at one point it wasn’t. Someone created the door pattern which included the door handle, the hinges and the placement of these components. Walk into any home and you can identify any door and it’s components. The styles and colors might be different, but the components are the same. Software is the same.

There are known software patterns to common software problems. In 1995, Design Patterns: Elements of Reusable Object-Oriented Software was published describing common software patterns. This book describes common problems encountered in most software application and offered an elegant way to solve these problems. Developers also create their own patterns while solving problems they routinely encounter. While they don’t publish a book, if you look close enough you can identify them.

Sometimes it’s difficult to identify the patterns. This makes grokking the code difficult. When you find yourself in this situation, inspect the code, see how it is used. Start a re-write. Ask yourself, how would you accomplish the same outcome. Often as you travel the thought process of an algorithm, you gain insight into the other developer’s implementation. Many of us have the inclination to re-write what we don’t understand. Resist this urge! The existing implementation is battle-tested and yours is not.

Some code is just vexing, reach out to a peer — a second set of eyes always helps. Walk the code together. You’ll be surprised what the two of you will find.

Here are 5 tips for leaving breadcrumbs for next developers

1. Patterns
Use known patterns, create your own patterns. Stick with a consistent paradigm throughout the code. For example, don’t have 3 approaches to data access.

2. Consistency
This is by far the most important aspect of coding. Nothing is more frustrating than finding inconsistent code. Consistency allows for assumptions. Each time a specific software pattern is encountered, it should be assumed it behaves similarly as other instances of the pattern.

Inconsistent code is a nightmare, imagine reading a book with every word meaning something different, including the same word in different places. You’d have to look up each word and expend large amounts of mental energy discovering the intent. It’s frustrating, tedious and painful. You’ll go crazy! Don’t do this to next developer.

3. Verbose Naming
This is your language. These are the words to your story. Weave them well.

This includes class names, method names, variable names, project names and property names.

Don’t:

if(monkey.HoursSinceLastMeal > 3)
{
    FeedMonkey();
}

Do:

int feedInterval = 3;

if(monkey.HoursSinceLastMeal > feedInterval)
{
    FeedMonkey();
}

The first example has 3 hard coded in the if statement. This code is syntactically correct, but the intent of the number 3 tells you nothing. Looking at the property it’s evaluated against, you can surmise that it’s really 3 hours. In reality we don’t know. We are making an assumption.

In the second example, we set 3 to a variable called ‘feedInterval’. The intent is clearly stated in the variable name. If it’s been 3 hours since the last meal, it’s time to feed the monkey. A side effect of setting the variable is we can now change the feed interval without changing the logic.

This is a contrived example, in a large piece of software this type of code is self documenting and will help the next developer understand the code.

4. Comments
Comments are a double edge sword. Too much commenting increases maintenance costs, not enough leaves developers unsure on how the code works. A general rule of thumb is to comment when the average developer will not understand the code. This happens when the assumptions are not obvious or the code is out of the ordinary.

5. Code Simple
In my professional opinion writing complex code is the biggest folly among developers.

Steve Jobs on simplicity:

Simple can be harder than complex: You have to work hard to get your thinking clean to make it simple. But it’s worth it in the end because once you get there, you can move mountains.

Complexity comes in many forms, some of which include: future proofing, overly complex implementations, too much abstraction, large classes and large methods.

For more on writing clean simple code, see Uncle Bob’s book Clean Code and Max Kanat-Alexander’s Code Simplicity

Closing

Reading code is hard. With a few simple steps you can ensure the next developer will grok your code.

Questions to Ask During an Interview

When I walk out of an interview, I want to know the position’s responsibilities, I want to know the environment and I want to know what I am expected to accomplish during my first week. Most of all I want to know if the company is a fit for me. More often than not companies will hire the best among the candidate pool. This does not mean they are the best for the position. Simply they are the best in the given candidate pool. Very few companies recognize this difference. It’s your job as the interviewee to vet the company.

I have developed the following questions to ask during an interview:

What will be my first task?
Is there a project plan? How much thought has gone into this position?

**What will determine success or failure? **
If project success can’t be articulated, how can they measure success in the position?

**How do I get my tasks? **
Is an issue tracking system used?

Do you use source control?
A company without source control in 2014 is almost always a deal breaker. If a company can’t provide the most basic need of software engineers there are bound to be other issues.

Do you allow remote work?
Telecommuting is a nice perk. It affords you flexibility to do errands or have appointments during lunch.

**Describe the computer/environment I am provide. **
What type of machine is given to software engineers? Two monitors or one? Is the work area low traffic and quiet — Getting stuck in a loud high traffic area sucks.

What are the hours?
Are the hours flexible? What are the core hours?

Am I on call?
Are you expected to support production issues during off hours? Do software engineers answer customer support calls?

Automated builds and Deployments?
How evolved is the build process? Do developers manually build or is it automated?

Do you have testers?
Am I responsible for testing?

**What technologies do you use? **
There are some technologies that are no longer interesting.
SCRUM, Lean, Agile or Waterfall. Does the team do Code Reviews? What about Unit Testing?

Most forget that an interview is a two way street. You, as the interviewee, are interviewing the company and your future co-workers for a good fit in the company and in the position.

Implementing Transparent Encryption with NHibernate Listeners (Interceptors)

Have you ever had to encrypt data in the database? In this post, I’ll explore how using nHibernate Listeners to encrypt and decrypt data coming from and going into your database. The cryptography will be transparent to your application.

Why would you want to do this? SQL Server has encryption baked into the product. That is true, but if you are moving to the cloud and want to use SQL Azure you’ll need some sort of cryptography strategy. SQL Azure does not support database encryption.

What is an nHibernate Listener? I think of a Listener as a piece of code that I can inject into specific extensibility points in the nHibernate persistence and data hydration lifecycle.

As of this writing the following extensibility points are available in nHibernate.

  • IAutoFlushEventListener
  • IDeleteEventListener
  • IDirtyCheckEventListener
  • IEvictEventListener
  • IFlushEntityEventListener
  • IFlushEventListener
  • IInitializeCollectionEventListener
  • ILoadEventListener
  • ILockEventListener
  • IMergeEventListener
  • IPersistEventListener
  • IPostCollectionRecreateEventListener
  • IPostCollectionRemoveEventListener
  • IPostCollectionUpdateEventListener
  • IPostDeleteEventListener
  • IPostInsertEventListener
  • IPostLoadEventListener
  • IPostUpdateEventListener
  • IPreCollectionRecreateEventListener
  • IPreCollectionRemoveEventListener
  • IPreCollectionUpdateEventListener
  • IPreDeleteEventListener
  • IPreInsertEventListener
  • IPreLoadEventListener
  • IPreUpdateEventListener
  • IRefreshEventListener
  • IReplicateEventListener
  • ISaveOrUpdateEventListener

The list is extensive.

To implement transparent cryptography, we need to find the right place to encrypt and decrypt the data. For encrypting the data we’ll use IPostInsertEventListener and IPostUpdateEventListener. With these events we’ll catch the new data and the updated data going into the database. For decrypting, we’ll use the IPreLoadEventListener.

For this demonstration we’ll be using DatabaseCryptography class for encrypting and decrypting. The cryptography implementation is not important for this article.

IPreLoadEventListener

public class PreLoadEventListener : IPreLoadEventListener
{
readonly DatabaseCryptography _crypto = new DatabaseCryptography();

///
/// Called when [pre load].
///

///The event. public void OnPreLoad(PreLoadEvent @event)
{
_crypto.DecryptProperty(@event.Entity, @event.Persister.PropertyNames, @event.State);
}
}

IPreInsertEventListener

public class PreInsertEventListener : IPreInsertEventListener
{
readonly DatabaseCryptography _crypto = new DatabaseCryptography();

///
/// Return true if the operation should be vetoed
///

///The event. /// true if XXXX, false otherwise.
public bool OnPreInsert(PreInsertEvent @event)
{
_crypto.EncryptProperties(@event.Entity, @event.State, @event.Persister.PropertyNames);

return false;
}
}

IPreUpdateEventListener

public class PreUpdateEventListener : IPreUpdateEventListener
{
readonly DatabaseCryptography _crypto = new DatabaseCryptography();

///
/// Return true if the operation should be vetoed
///

///The event. /// true if XXXX, false otherwise.
public bool OnPreUpdate(PreUpdateEvent @event)
{
_crypto.EncryptProperties(@event.Entity, @event.State, @event.Persister.PropertyNames);

return false;
}
}

It’s important to note that on both IPreUpdateEventListener and IPreInsertEventListener must return false, otherwise the insert/update event will be aborted.

Now that we have the Listeners implemented we need to register them with nHibernate. I am using FluentNHibernate so this will be different if you are using raw nHibernate.

SessionFactory

public class SessionFactory
{
///
/// Creates the session factory.
///

/// ISessionFactory.
public static ISessionFactory CreateSessionFactory()
{
return Fluently.Configure()

.Database(MsSqlConfiguration.MsSql2012
.ConnectionString(c => c
.FromConnectionStringWithKey("DefaultConnection")))

.Mappings(m => m.FluentMappings.AddFromAssemblyOf())
.ExposeConfiguration(s =>
{
s.SetListener(ListenerType.PreUpdate, new PreUpdateEventListener());
s.SetListener(ListenerType.PreInsert, new PreInsertEventListener());
s.SetListener(ListenerType.PreLoad, new PreLoadEventListener());
})
.BuildConfiguration()
.BuildSessionFactory();
}

When decrypting and encrypting data at the application level it makes the data useless in the database. You’ll need to bring the data back into the application to read the values of the encrypted fields. We want to limit the fields that are encrypted and we only want to encrypt string values. Encrypting anything other that string values complicates things. There is nothing saying we can’t encrypt dates, but doing so will require the date field in the database to become a string(nvarchar or varchar) field, to hold the encrypted data, once we do this we lose the ability to operate on the date field from the database.

To identify which fields we want encrypted and decrypted I’ll use marker attributes.

Encrypt Attribute

public class EncryptAttribute : Attribute
{
}

Decrypted Attribute

public class DecryptAttribute : Attribute
{
}

To see the EncryptAttribute and the DecryptedAttribute in action we’ll take a peek into the DatabaseCryptography class.

DatabaseCryptography

public class DatabaseCryptography
{
    private readonly Crypto _crypto = ObjectFactory.GetInstance();

    ///
    /// Encrypts the properties.
    ///
    ///The entity. ///The state. ///The property names. 
    public void EncryptProperties(object entity, object[] state, string[] propertyNames)
    {
        Crypt(entity, propertyNames, s = >
        _crypto.Encrypt(s),
        state)
        ;
    }

    ///
    /// Crypts the specified entity.
    ///

    ///
    ///The entity. ///The state. ///The property names. ///The crypt.
    private void Crypt(object entity, string[] propertyNames, Func<string, string> crypt, object[] state) where T : Attribute
    {
        if (entity != null)
        {
            var properties = entity.GetType().GetProperties();

            foreach (var info in properties)
            {
                var attributes = info.GetCustomAttributes(typeof (T), true);

                if (attributes.Any())
                {
                    var name = info.Name;
                    var count = 0;

                    foreach (var s in propertyNames)
                    {
                        if (string.Equals(s, name, StringComparison.InvariantCultureIgnoreCase))
                        {
                            var val = Convert.ToString(state[count]);
                            if (!string.IsNullOrEmpty(val))
                            {

                                val = crypt(val);
                                state[count] = val;
                            }

                            break;
                        }

                        count++;
                    }
                }
            }
        }
    }

    ///
    /// Decrypts the property.
    ///
    ///The entity. ///The state. ///The property names. 
    public void DecryptProperies(object entity, string[] propertyNames, object[] state)
    {
        Crypt(entity, propertyNames, s = >
        _crypto.Decrypt(s),
        state)
        ;
    }

}

That’s it. Now the encryption and decryption of data will be transparent to the application and you can go on your merry way building the next Facebook.

Missing Management Delegation Icon in IIS

It’s critical this is done first. Web deploy may not install correctly if it’s installed with the Management Service icon missing. Check IIS for the Management Delegation icon, it’ll be under the Management section.

If it’s missing run the following commands.

Windows 2012

dism /online /enable-feature /featurename:IIS-WebServerRole
dism /online /enable-feature /featurename:IIS-WebServerManagementTools
dism /online /enable-feature /featurename:IIS-ManagementService
Reg Add HKLM\Software\Microsoft\WebManagement\Server /V EnableRemoteManagement /T REG_DWORD /D 1
net start wmsvc
sc config wmsvc start= auto

Run Web Deploy.

Check to see if the icon is there. If it’s not, run web deploy again. It should be there.

Calling Stored Procedures with Code First

One of the weaknesses of Entity Framework 6 Code First is the lack of support for natively calling database constructs (views, stored procedures… etc). For those who have not heard of or used Code-First in Entity Framework (EF), Code-First is simply a Fluent mapping API. The idea is to create all your database mappings in code (i.e. C#) and the framework then creates and track the changes in the database schema.

In traditional Entity Framework to call a stored procedure you’d map it in your EDMX file. This is a multi-step process. Once the process is completed a method is created, which hangs off the DataContext.

I sought to making a calling stored procedure easier. At the heart of a stored procedure you have a procedure name, N number of parameters and a results set. I’ve written a small extension method that takes a procedure name, parameters and a return type. It just works. No mapping the procedure and it’s parameters.

public static List<TReturn> CallStoredProcedure<TParameters, TReturn>(this DataContext context, string storedProcedure, TParameters parameters) where TParameters : class where TReturn : class, new()
{
IDictionary<string,object> procedureParameters = new Dictionary<string, object>();
PropertyInfo[] properties = parameters.GetType().GetProperties();

var ps = new List<object>();

foreach (var property in properties)
{
object value = property.GetValue(parameters);
string name = property.Name;

procedureParameters.Add(name, value);

ps.Add(new SqlParameter(name, value));
}

var keys = procedureParameters.Select(p => string.Format("@{0}", p.Key)).ToList();
var parms = string.Join(", ", keys.ToArray());

return context.Database.SqlQuery<TReturn>(storedProcedure + " " + parms, ps.ToArray()).ToList();
}

Usage

var context = new DataContext();

List<User> users = context.CallStoredProcedure<object,User>("User_GetUserById", new{userId = 3});
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