c# 条件编译 Conditional ("DEBUG")

c# 条件编译 Conditional ("DEBUG")

简而言之：可以通过Conditional 指定函数和属性是否编译到最终产品中去。同时还应该看看 AttributeUsage Obsolete

C# Language Specification

• System.AttributeUsageAttribute (Section 17.4.1), which is used to describe the ways in which an attribute class can be used.
• System.Diagnostics.ConditionalAttribute (Section 17.4.2), which is used to define conditional methods.
• System.ObsoleteAttribute (Section 17.4.3), which is used to mark a member as obsolete.

//z 2012-2-24 17:47:38 PM is2120@csdn
利用 Conditional 属性，程序员可以定义条件方法。Conditional 属性通过测试条件编译符号来确定适用的条件。当运行到一个条件方法调用时，是否执行该调用，要根据出现该

调用时是否已定义了此符号来确定。如果定义了此符号，则执行该调用；否则省略该调用（包括对调用的参数的计算）。

条件方法要受到以下限制：

条件方法必须是类声明或结构声明中的方法。如果在接口声明中的方法上指定 Conditional 属性，将出现编译时错误。
条件方法必须具有 void 返回类型。
不能用 override 修饰符标记条件方法。但是，可以用 virtual 修饰符标记条件方法。此类方法的重写方法隐含为有条件的方法，而且不能用 Conditional 属性显式标记。
条件方法不能是接口方法的实现。否则将发生编译时错误。

A conditional method is subject to the following restrictions:

• The conditional method must be a method in a class or struct declaration. A compile-time error occurs if theConditional attribute is specified on a method in an interface declaration.
• The conditional method must have a return type of void.
• The conditional method must not be marked with the override modifier. A conditional method may be marked with thevirtual modifier, however. Overrides of such a method are implicitly conditional, and must not be explicitly marked with aConditional attribute.
• The conditional method must not be an implementation of an interface method. Otherwise, a compile-time error occurs.

In addition, a compile-time error occurs if a conditional method is used in a delegate-creation-expression.

//z 2012-2-24 17:47:38 PM is2120@csdn
示例1：
// CondMethod.cs
// compile with: /target:library /d:DEBUG
using System;
using System.Diagnostics;
namespace TraceFunctions
{
   public class Trace
   {
       [Conditional("DEBUG")]
       public static void Message(string traceMessage)
       {
           Console.WriteLine("[TRACE] - " + traceMessage);
       }
   }
}

示例2：

using System;

using System.Diagnostics;

public classTrace

{

    [Conditional("DEBUG")]

    publicStaticvoidShowMessage(stringmsg)

    {

        Console.WriteLine(" [Trace - "+ msg);

    }

}

public classProgram

{

    publicstaticvoidMain()

    {

        Trace.ShowMessage("Starting");

        Console.WriteLine("运行中");

        Trace.ShowMessage("Ending");

    }

}

//z 2012-2-24 17:47:38 PM is2120@csdn