Chapter 23. Diagnostics

When things go wrong, it’s important that information is available to aid in diagnosing the problem. An IDE or debugger can assist greatly to this effect—but it is usually available only during development. Once an application ships, the application itself must gather and record diagnostic information. To meet this requirement, the .NET Framework provides a set of facilities to log diagnostic information, monitor application behavior, detect runtime errors, and integrate with debugging tools if available.

The types in this chapter are defined primarily in the System.Diagnostics namespace.

Conditional Compilation

You can conditionally compile any section of code in C# with preprocessor directives. Preprocessor directives are special instructions to the compiler that begin with the # symbol (and, unlike other C# constructs, must appear on a line of their own). The preprocessor directives for conditional compilation are #if, #else, #endif, and #elif.

The #if directive instructs the compiler to ignore a section of code unless a specified symbol has been defined. You can define a symbol with either the #define directive or a compilation switch. #define applies to a particular file; a compilation switch applies to a whole assembly:

#define TESTMODE            // #define directives must be at top of file
                            // Symbol names are uppercase by convention.
using System;

class Program
  static void Main(  )
    Console.WriteLine ("in test mode!");     // OUTPUT: in test mode!
#endif ...

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