return error message with "Throw Exception" or "Return"?

The 2 options have a different purpose, the first using throw serves to throw an exception in our application.

try
{
    .......
 return  cargarPersonas;
}
catch(Exception e)
{
    throw  new Exception("Mensaje.", e);
}

and the second option returns a String containing the error message:

try
{
    .......
 return  cargarPersonas;
}
catch(Exception e)
{
    return "Mensaje: " + e.message;
}

If you just want to return a message:

  

What is the best way to return a message in the case that arises   an error?

the ideal option would be the second option.

According to Microsoft's guide , the following are given recommendations:

• Avoid returning error codes
• Report errors throwing exceptions.
• If an error occurs in which it is dangerous to continue with the execution of the program, the execution must be terminated.
• Do not use exceptions for normal flow control.
• Document exceptions.
• Do not return method exceptions
• Consider using builders for exceptions.

Among others that can be seen in the official guide.

Clearly throw the exception. That is, the first option.

The method that is responsible for collecting the exception will have a complete Exception object with all its properties including the descriptive message.

The method that collects the exception may control it or re-launch it to a higher level if it can not handle it.

The first option is more accurate in case you need to propagate the error to higher layers, however I do not recommend that you create a new Exception object.

The drawback of the second option is that you can only return a message when your method returns a string.

What you should do is:

If you know in advance that under certain conditions, an operation can fail, it is better that you throw the exception:

if(empleado == null || empleado.nombre == null) throw new InvalidOperationException("Mensaje relacionado a objetos de empleados no inicializados");

if(empleado.id < 0) throw new InvalidOperationException(string.Format("Mensake de Id no válido: {0}", empleado.nombre));

which will allow you to have a try / catch that will only propagate the errors:

try{ }catch{ throw; }

Which is basically the same as:

try{ }catch(Exception exc) { throw exc; }

What you should not do is:

try{ }catch(Exception exc) { throw new Exception("Mensaje"); }

Since you would be overwriting valuable information about the cause of the exception and sending only a message that will surely be something like: "failed to load users" without really having information about the type of exception or a clear message of the cause of the error .