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C# C# Objects Inheritance Exception Messages

Does anyone know how this Exception message was generated from Game.cs?

I am a little confused about how in this example... Console.WriteLine(ex.Message); … how was ex.Message able to genereate the string message from MapLocation.cs

What I'm mostly confused about is where we find the mysterious 'Message' …. from 'ex.Message' Console.WriteLine(); above …. I don't see 'Message' anywhere in any of our files.

I don’t remember exactly where you are here, but the honest answer here is it depends.

Some exceptions are thrown automatically by the .NET Framework's common language runtime (CLR) when basic operations fail. I’m guessing since you don’t know were they came from you didn’t create them. Creating you own exceptions will probably be dealt with later on.

Check out the MSDN for more info, https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/exceptions/

2 Answers

Steven Parker
Steven Parker
229,920 Points

The "Message" property is part of the exception object that is created by the system when an error occurs or when you perform a "throw". The argument passed to "throw" gets loaded into the "Message" property by the system. This property can then be accessed when the exception is caught in the parameter "ex".

For more details, see the MSDN page for Exception.Message.

Stephen Cole
PLUS
Stephen Cole
Courses Plus Student 15,809 Points

There are a number of properties returned when an exception is returned.

Message is the text from the constructor we created.

I'm guessing that string interpolation was not yet a thing when this video was first created. Here's my code.

namespace TreehouseDefense
{
    class MapLocation : Point
    {
        public MapLocation(int x, int y, Map map) : base(x, y)
        {
            if (!map.OnMap(this))
            {
                throw new System.Exception($"({x}, {y}) is outside of the map's boundaries.");
            }
        }
    }
}

The Message returned in my code is $"({x}, {y}) is outside of the map's boundaries."

This gives me a chance to return a message that has meaning and/or context.

Here's a link with more information about the other properties returned: https://docs.microsoft.com/en-us/dotnet/standard/exceptions/exception-class-and-properties