Refactoring a 3000‑Line C# System to 15 Lines: Lessons and Practices

The author, a recent graduate who joined a data‑center monitoring company, was tasked with maintaining a large ASP.NET/WebForms client written in a classic three‑tier architecture. The original codebase contained massive factory classes with repetitive boilerplate for each new table, leading to tedious manual updates.

Refactor 3000 Lines of Code to 15 Lines

By noticing that the className generation and its return type were closely related, the author explored reflection and generics to replace the repetitive factory methods. The resulting implementation reduced dozens of screens of code to a handful of concise, generic methods.

Although concerned that reducing line count might affect software‑copyright evaluation, the refactored code proved stable and eliminated copy‑paste errors.

Use Code Generators Sparingly

The author analyzes why the original code was so verbose: heavy reliance on a code‑generation tool (Dongsoft) and a blind copy‑paste approach. He argues that most repetitive work can be handled by the framework itself, and only simple model classes truly need generation.

for (int n = 0; n < rowsCount; n++)
{
    model = new DBAccess.Model.eventweek();
    if (dt.Rows[n]["GroupNo"].ToString() != "")
    {
        model.GroupNo = int.Parse(dt.Rows[n]["GroupNo"].ToString());
    }
    // ... similar blocks for Week0, Week1, etc.
}

He suggests rewriting such logic using built‑in utilities like String.Split or custom helpers, and recommends tools such as CodeSmith for more controlled template generation.

Consider Refactoring Before Rewriting

Rewriting an entire system often leads to over‑design, compatibility issues, and wasted effort. Instead, the author advocates incremental refactoring: extract registration logic into reflection‑based factories, decouple business code from the core engine, and keep interfaces stable.

private void RegisterTaskHandlerBundles()
{
    var bundles = ServiceBundleCache.Instance.GetBundles("TaskHandlerBundle");
    if (bundles != null && bundles.Count > 0)
    {
        var asmCache = new Dictionary<string, Assembly>();
        foreach (var bundle in bundles)
        {
            try
            {
                if (!asmCache.ContainsKey(bundle.Category))
                    asmCache.Add(bundle.Category, Assembly.Load(bundle.AssemblyName));
                var handler = (ITaskHandler)asmCache[bundle.Category]
                    .CreateInstance(bundle.ClassName, false, BindingFlags.Default, null,
                        new object[] { this, bundle }, null, null);
                _taskHandlerBundles.Add(bundle, handler);
            }
            catch (Exception e)
            {
                NLogHelper.Instance.Error("Failed to load bundle [{0}]", bundle.Name, e.Message);
            }
        }
    }
}

With this approach, adding a new feature only requires implementing the appropriate interface and inserting a record into the configuration table, leaving the core engine untouched.

Learn Unit Testing to Foster Refactoring Mindset

The author promotes unit testing as a practical way to encourage refactoring. By making methods testable—single‑purpose, low‑coupling, and parameter‑driven—developers naturally improve code quality and become more comfortable with restructuring code.

He distinguishes his approach, called TDR (Test‑Driven Refactoring) , from full‑blown TDD, emphasizing that tests are a means to guide clean‑up rather than a prerequisite for every feature.

What Refactoring Really Means

Strengthen fundamentals.

Read high‑quality code.

Avoid copy‑paste; eliminate duplication.

Reduce reliance on code generators.

Prefer refactoring over rewriting.

Make every method testable.

Following these principles leads to smaller, more stable, and reusable code, while simultaneously improving one’s ability to read, write, and architect software systems.

For readers interested in deeper topics, the author suggests exploring reflection, IoC, and plugin architectures.