Conditional Attribute in C#: What It Is and How It Works

The Conditional attribute in C# lets you include or exclude method calls based on whether a specified compilation symbol is defined. It is mainly used to control debugging or logging code without removing it from the source.

How It Works

The Conditional attribute works like a traffic light for method calls. When you mark a method with this attribute and specify a symbol name, the compiler checks if that symbol is defined. If it is, calls to that method stay in the compiled program; if not, those calls are removed entirely.

Think of it like a switch that turns certain code on or off depending on the build settings. This helps keep your code clean and efficient by including extra code only when needed, such as during debugging or testing, without changing the method itself.

Example

This example shows a method marked with [Conditional("DEBUG")]. It only runs when the DEBUG symbol is defined, usually in debug builds.

csharp

using System;
using System.Diagnostics;

class Program
{
    [Conditional("DEBUG")]
    static void Log(string message)
    {
        Console.WriteLine("LOG: " + message);
    }

    static void Main()
    {
        Log("Starting the program.");
        Console.WriteLine("Hello, World!");
        Log("Ending the program.");
    }
}

Output

LOG: Starting the program.
Hello, World!
LOG: Ending the program.

When to Use

Use the Conditional attribute when you want to include code only in certain builds, like debug or testing, without cluttering your release version. It is perfect for logging, tracing, or diagnostic methods that help during development but are unnecessary or unwanted in production.

This way, you avoid manually commenting out or deleting code and reduce the risk of accidentally shipping debug code in your final product.

Key Points

• The Conditional attribute controls whether calls to a method are included based on a compilation symbol.
• It only works on methods that return void.
• Commonly used for debug or trace logging methods.
• Helps keep production code clean without removing debug code.

Key Takeaways

The Conditional attribute includes or removes method calls based on defined symbols.

It is mainly used for debug or logging methods to avoid cluttering release builds.

Only methods with void return type can use the Conditional attribute.

It helps keep code clean by automatically excluding code in certain builds.