What is Explicit Compilation?

Explicit compilation in the context of .NET and ASP.NET refers to the process where the source code is compiled into machine code prior to the execution of the program. This is in contrast to implicit compilation, where the code is compiled just-in-time (JIT) during execution.

Key Points of Explicit Compilation:

1. Pre-Execution Compilation:

   • Explicit compilation involves converting the source code into machine code before the program runs. This is typically done using an Ahead-of-Time (AOT) compiler[5][6].

2. Deployment:

   • In the case of ASP.NET Web Application Projects (WAPs), explicit compilation means that the web application's code is compiled into a single assembly, which is then deployed along with the markup content. The code-behind class files do not need to be deployed as they are already compiled into the assembly[1].

3. Advantages:

   • Performance: Since the code is already compiled, there is no need for the runtime to compile the code, which can lead to faster startup times.
   • Security: The source code is not deployed, which can help protect intellectual property and reduce the risk of code tampering.
   • Portability: The compiled code can be optimized for specific platforms, potentially improving performance and compatibility.

4. Examples in .NET:

   • Native AOT: .NET 8 introduces support for Native AOT (Ahead-of-Time) compilation, which compiles Intermediate Language (IL) code to native code before execution. This is particularly useful for creating self-contained applications that do not require a separate runtime[15].
   • Ngen.exe: The Native Image Generator (Ngen.exe) is an example of a tool used for explicit compilation in .NET, which pre-compiles assemblies to native code to improve startup performance[6].

5. Configuration:

   • In .NET Core, explicit compilation can be configured using project settings. For example, setting <PublishAot>true</PublishAot> in the project file enables Native AOT compilation during the publish process[15].

Example of Explicit Compilation in .NET Core:

To enable Native AOT compilation in a .NET Core project, you can modif...