I gather that
object k = 999;
If you have a look at http://referencesource.microsoft.com/#mscorlib/system/console.cs,8c83114cc3fd109d
then you'll see that there are many overloads of the
WriteLine function in the
Console class, including
Console.WriteLine(Object value). This is very convenient.
MessageBox.Show lacks these different overloads and excepts "only" a string.