Proper design is a major factor that contributes to the scalability and performance of any application.
Topics: 
   * Efficient Resource Management
   * Considerations for Crossings the Application Boundary
   * Single Large Assemblies or Multiple Smaller Assemblies
   * Code Refactoring by Logical Layers
   * Threads are a Resource worth Sharing

My article on C# .NET Application Design Considerations can be read here

This article talks about best practices of exception handling, and guides you for some common programming mistakes developers do, as that seems appropriate in most of the application written.

Read full article Best Practices – Exception Handling

Validation is a process that ensures the sanity of data entered, received or processed by a software module, class or class members.  Some examples of validation are length check, range check, Null check, date range, specific character and so on.

Read full Article here: Validation Application Block