How to show non implemented methods in API without throwing an exception and prevent compilation

Question

I am writing a core API that will be used by client developer.

There are some methods that are still not developed but I need them to be in the API so the developer can see them in the Intellisense.

In addition to the API documentation I am providing to the developer, I need him to know during the development that a method is not yet implemented but it exist.

Is there a way to inform the developer that the method is not yet implemented without throwing NotImplementedException and if he will try to use the method it will not compile?

For example:

public class API
{
    public void PrintToPDF()
    {
          // do not throw NotImplementedException
    }
}


public class Client
{
     public void Print()
     {
          API api = new API();
          api.PrintToPDF();        // shouldn't compiled but can be see in intellisense. It can show a tooltip that it is in being developed. 
     }
}

Answer 1

Use the obsolete attribute, it can generate both a warning or an error as you define it.

using System;
using System.Reflection;

public class Example
{
   // Mark OldProperty As Obsolete.
   [ObsoleteAttribute("This property is for future use", false)] 
   public static string OldProperty
   { get { return "The old property value."; } }

   public static string NewProperty
   { get { return "The new property value."; } }

   // Mark CallOldMethod As Obsolete.
   [ObsoleteAttribute("This method is for future use", true)] 
   public static string CallOldMethod()
   {
      return "You have called CallOldMethod.";
   }

   public static string CallNewMethod() 
   {   
      return "You have called CallNewMethod.";
   }   

   public static void Main()
   {                 
      Console.WriteLine(OldProperty);
      Console.WriteLine();
      Console.WriteLine(CallOldMethod());
   } 
}
// The attempt to compile this example produces output like the following output:
//    Example.cs(31,25): error CS0619: 'Example.CallOldMethod()' is obsolete: 
//            'This method is for future use'
//    Example.cs(29,25): warning CS0618: 'Example.OldProperty' is obsolete: 
//            'This property is for future use'

You can also create your own attribute.

[Obsolete("Reserved for future use", true)]
public class ReservedForFutureUse : System.Attribute
{

}