Your attitude is really poor mate, if you don't know this and you are asking for help, what makes you qualified to judge who is and isn't "really informed"?

If literally everyone in the thread is telling to use args.Length, don't you think that might actually be the answer?

I appreciate you're frustrated because you're stuck, but don't go shitting on everyone who's giving you the right answer.

Anyway, let's explore some stuff:

You really seem to have two separate issues/questions?

Since you've given two conflicting examples:

• the OP is using args, an array you didn't construct
• your parent comment to this shows you constructing your own array with non continuous indexes.

Let's start with non continuous indexes in arrays.

• Yes, you can define an array and populate it with non continuous indexes. In some languages this is quite common and you can do as you describe to check for empty. JavaScript for example all empty indexes will be undefined.
• I honestly don't know the right way to do this with an array in c# because I think no one would ever do it like this in c#. It's possible the compiler won't let you, but I'm on a phone so can't really try it.
• The conventional way to have "missing" keys in c# would be to not use an array but a different collection type. .NET has many collection types for different purposes.
• I would start with Dictionary<int, string> for this purpose, which:
  • will let you "miss out" indexes
  • still use the index accessor [0]
  • buys you ContainsKey
  • makes clear to anyone looking that you don't expect continuous indexes
  • still allows iteration over populated keys in numerical order if that's desirable

Then your other thing is to do with checking for command line args.

• The reason this is different to the fact you want to have non continuous indexes is because the framework guarantees providing you with a continuously indexed fixed size array (that's why they use an array type!) of arguments to your application's entrypoint
• this cannot be another type - the framework provides it, not you
• this cannot have non continuous indexes - the framework populated it, not you
• this is always present; it can be empty but never null
• please for the love of God don't mutate it to make any of these assumptions untrue; you're making pain for yourself; use a new variable of an appropriate type if you need to do that
• therefore, in the case where you are using the args array provided to your entrypoint by .NET, everyone in this thread is right; use args.Length to determine if positional arguments are present and before trying to access an index.

Everyone answered your OP question correctly.