Beginner-to-Advanced VB.NET Code Library: Best Practices & SamplesBuilding a well-organized VB.NET code library bridges the gap between learning the language and producing reliable, maintainable applications. This article walks you from beginner-friendly snippets to advanced patterns and best practices, with concrete examples you can copy, adapt, and add to your personal library.
Why a VB.NET code library matters
A curated code library saves time, reduces bugs, and enforces consistency across projects. Rather than searching forums for a solution each time, a library gives you vetted, reusable components that reflect your team’s conventions and architectural choices.
Organizing the library
A practical structure scales with project complexity. Suggested top-level folders:
- Utilities (string, date, file helpers)
- Data (ORM helpers, DTOs, repositories)
- Services (API clients, background workers)
- UI (WinForms/WPF helpers, custom controls)
- Patterns (factories, dependency injection, unit of work)
- Tests (unit/integration test helpers and mocks)
Use logical namespaces that mirror folders, e.g., MyLib.Utilities.Strings.
Style & conventions (best practices)
- Follow .NET naming conventions: PascalCase for types and methods, camelCase for parameters and private fields.
- Keep methods small and single-responsibility.
- Favor immutable data where practical (ReadOnly properties, immutable DTOs).
- Use Option (Nullable) patterns and explicit null checks to avoid NullReferenceException.
- Document public members with XML comments (///).
- Use regions sparingly; prefer well-named classes and files.
- Add unit tests for all public behaviors.
- Provide examples and README per module.
Versioning, packaging, and distribution
- Semantic Versioning (MAJOR.MINOR.PATCH).
- Use Git for source control and tags for release points.
- Publish reusable packages as NuGet packages with clear metadata and changelogs.
- Include LICENSE and CONTRIBUTING files for open-source libraries.
Beginner samples
These give beginners immediate value and show common VB.NET idioms.
1) Safe string trimming and emptiness check
Public Module StringHelpers Public Function IsNullOrWhiteSpace(value As String) As Boolean Return String.IsNullOrWhiteSpace(value) End Function Public Function SafeTrim(value As String) As String If value Is Nothing Then Return String.Empty Return value.Trim() End Function End Module 2) Simple file logger
Imports System.IO Public Class FileLogger Private ReadOnly _path As String Public Sub New(path As String) _path = path End Sub Public Sub Log(message As String) Dim line = $"{DateTime.UtcNow:O} - {message}" SyncLock _path File.AppendAllLines(_path, New List(Of String) From {line}) End SyncLock End Sub End Class 3) Basic HTTP GET (HttpClient wrapper)
Imports System.Net.Http Imports System.Threading.Tasks Public Class SimpleHttpClient Private Shared ReadOnly _client As New HttpClient() Public Shared Async Function GetStringAsync(url As String) As Task(Of String) Return Await _client.GetStringAsync(url) End Function End Class Intermediate samples
Introduce patterns, error handling, and better abstractions.
1) Repository pattern with a simple in-memory implementation
Public Interface IRepository(Of TKey, TEntity) Function GetById(id As TKey) As TEntity Sub Add(entity As TEntity) Sub Remove(id As TKey) Function List() As IEnumerable(Of TEntity) End Interface Public Class InMemoryRepository(Of TKey, TEntity) Implements IRepository(Of TKey, TEntity) Private ReadOnly _store As New Dictionary(Of TKey, TEntity)() Public Sub Add(entity As TEntity) Implements IRepository(Of TKey, TEntity).Add Dim idProp = GetType(TEntity).GetProperty("Id") If idProp Is Nothing Then Throw New InvalidOperationException("Entity must have Id property") Dim id = DirectCast(idProp.GetValue(entity), TKey) _store(id) = entity End Sub Public Function GetById(id As TKey) As TEntity Implements IRepository(Of TKey, TEntity).GetById Return If(_store.ContainsKey(id), _store(id), Nothing) End Function Public Sub Remove(id As TKey) Implements IRepository(Of TKey, TEntity).Remove If _store.ContainsKey(id) Then _store.Remove(id) End Sub Public Function List() As IEnumerable(Of TEntity) Implements IRepository(Of TKey, TEntity).List Return _store.Values End Function End Class 2) Retry helper for transient faults
Imports System.Threading Public Module RetryHelper Public Function Retry(Of T)(attempts As Integer, delayMs As Integer, action As Func(Of T)) As T Dim lastEx As Exception = Nothing For i = 1 To attempts Try Return action() Catch ex As Exception lastEx = ex Thread.Sleep(delayMs) End Try Next Throw lastEx End Function End Module Advanced patterns & samples
Focus on architecture, performance, and integration scenarios.
1) Dependency Injection with Microsoft.Extensions.DependencyInjection
Example of registering services:
Imports Microsoft.Extensions.DependencyInjection Public Module ServiceRegistration Public Sub ConfigureServices(services As IServiceCollection) services.AddSingleton(Of IMyService, MyService)() services.AddTransient(Of IRepository(Of Integer, MyEntity), InMemoryRepository(Of Integer, MyEntity))() End Sub End Module 2) Async streams (IAsyncEnumerable) consumption
Imports System.Collections.Generic Imports System.Threading Imports System.Threading.Tasks Public Module AsyncStreamExamples Public Async Function ProduceAsync(cancellation As CancellationToken) As IAsyncEnumerable(Of Integer) Dim i As Integer = 0 While Not cancellation.IsCancellationRequested Yield i i += 1 Await Task.Delay(100, cancellation) End While End Function End Module 3) High-performance memory pooling example (ArrayPool)
Imports System.Buffers Public Module BufferHelpers Public Function RentBuffer(size As Integer) As Byte() Return ArrayPool(Of Byte).Shared.Rent(size) End Function Public Sub ReturnBuffer(buffer As Byte()) ArrayPool(Of Byte).Shared.Return(buffer) End Sub End Module Testing strategies
- Unit tests: small, fast, isolated. Use NUnit/xUnit/MSTest.
- Integration tests: exercise external dependencies (DB, API); run in CI with dedicated test resources.
- Use test doubles (mocks/fakes) for services.
- Cover edge cases and failure paths — not just happy paths.
Security & error-handling
- Never log sensitive data (passwords, tokens).
- Validate all inputs; use parameterized queries or ORMs to prevent SQL injection.
- Use try/catch sparingly; prefer exception propagation with meaningful custom exceptions.
- Apply principle of least privilege for file/DB access.
Performance tips
- Avoid unnecessary allocations; reuse buffers via ArrayPool.
- Prefer StringBuilder for heavy string concatenation.
- Cache expensive computations (MemoryCache).
- Use asynchronous IO to keep threads free.
Documentation & examples
- Provide README with quickstart and code snippets for each module.
- Add XML comments and generate API docs (DocFX or Sandcastle).
- Include runnable samples or a Samples project that demonstrates common scenarios.
Sample library README snippet
Basic content to include in each module README:
- Purpose of the module
- Installation (NuGet or project reference)
- Quickstart snippets (copy/paste)
- Public API summary
- Contributing and tests
Putting it together: minimal starter template
Project structure:
- src/
- MyLib.Core/
- MyLib.Data/
- MyLib.Web/
- tests/
- MyLib.Core.Tests/
- samples/
- ConsoleSample/
- README.md
- LICENSE
Add CI pipeline to run tests and publish packages automatically on tag.
Closing notes
A useful VB.NET code library balances simplicity and correctness. Start with well-tested utilities, grow with patterns (DI, repositories, factories), and document everything. Over time you’ll replace ad-hoc snippets with robust, tested components that accelerate development and reduce bugs.
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