Is it possible to write Unmanaged Code in c++/.net on visual studio?

Yes, it is possible to write unmanaged code in C++ for .NET applications using Visual Studio. In the context of .NET, unmanaged code typically refers to code that is not managed by the Common Language Runtime (CLR). Unmanaged code might include native C++ code, legacy code, or code that directly interacts with the operating system.

Here are the steps to write unmanaged code in C++ for a .NET application:

1. **Create a C++ Project:**
   - Open Visual Studio and create a new project.
   - Choose a project template that corresponds to your needs. For example, you might choose "Empty Project" or "Windows Desktop Wizard" if you are creating a native Windows application.

2. **Write Unmanaged C++ Code:**
   - Add C++ files to your project and write unmanaged C++ code. This code will not be managed by the .NET runtime and can include standard C++ features and libraries.

3. **Compile as Native Code:**
   - Configure your project settings to compile the C++ code as native code (unmanaged). This can typically be done in the project properties under "Configuration Properties" > "General" > "Common Language Runtime Support." Set this option to "No Common Language Runtime Support" or "Pure MSIL Common Language Runtime Support."

4. **Interact with Managed Code:**
   - If your unmanaged C++ code needs to interact with managed (.NET) code, you can use interoperability mechanisms such as Platform Invocation Services (P/Invoke) or the Common Object File Format (COFF). P/Invoke allows you to call functions defined in managed assemblies from unmanaged code.

   ```cpp
   // Example of P/Invoke in C++
   #include <windows.h>

   extern "C" __declspec(dllexport) void CallManagedFunction();

   int main()
   {
       CallManagedFunction();
       return 0;
   }
   ```

   - You can define a managed function in a .NET language (e.g., C#) and call it from your unmanaged C++ code.

   ```csharp
   // Managed C# code
   using System;

   public class ManagedClass
   {
       public static void ManagedFunction()
       {
           Console.WriteLine("Managed function called.");
       }
   }
   ```

5. **Compile and Link:**
   - Compile your C++ code and link it with any necessary libraries. If you're using P/Invoke, ensure that the managed assembly (containing the managed function) is available to your unmanaged C++ application.

6. **Run the Application:**
   - Run the compiled unmanaged C++ application. If you've correctly configured the project to produce unmanaged code, it should run without relying on the .NET runtime.

Remember that unmanaged code lacks the safety features provided by managed code, so extra care is needed to handle memory, resource management, and other low-level aspects. Always consider the potential risks and benefits when combining unmanaged and managed code in a project.