ASP.NET: Can't switch web application into DEBUG mode

I have an ASP.NET 3.5 web application. For the application:

• Configuration set to "DEBUG;
• "Define DEBUG constant" checkbox is checked for "DEBUG" configuration;
• web.config file contains 'true' as v开发者_开发百科alue for 'debug' attribute of 'compilation' node.

Nevertheless to everything the following code:

#if ( _DEBUG )
    const bool DebugMode = true; 
#else
    const bool DebugMode = false;
#endif
string strSettings = string.Concat("(DebugMode: ", DebugMode, ")");

put "DebugMode: False" into result string. In the same time I can't connect to the application with VisualStudio in debug mode...

Question:

how can I get real value of debugging mode?

Is this C#? The constant is DEBUG, not _DEBUG.

Do you compile the website as a Web Application?

Your _DEBUG constant for Compile Pre-Processor directives are set by Visual Studio and passed to the compiler like this

csc /define:_DEBUG

But when you access the website its normally not compiled by Visual Studio, but the asp_net compiler and it only looks at the debug-attribute of the compilation section. You can check the value of this attribute at runtime using

HttpContext.Current.IsDebuggingEnabled

If you REALLY need Symbols defined in your webpages, you can pass /define arguments to the compiler by specifying it in web.config

<configuration>
   <system.web>
      <compilation debug="true">
         <compilers>
            <compiler language="C#;Csharp" compilerOptions="d:_DEBUG"/>
         </compilers>
      </compilation>
   </system.web>
</configuration>