Parameter changes original value

Question

I guess it is stupid question but if You can take a look

Here is my method

 public Tuple CheckRoyalFlush() { List<Honours> flush = new List<Honours>() { Honours.Ace, Honours.King, Honours.Queen, Honours.Jack, Honours.Ten }; if (RoyalFlushJokerHelper(honoursOnTheScreen, flush) || ContainsAllItems(honoursOnTheScreen, flush)) { Suits suit = cardsOnTheScreen.ElementAt(0).GetSuit(); foreach (Card card in cardsOnTheScreen.Skip(1)) { if (card.GetSuit() != suit) { if (card.GetHonour() == Honours.Joker) continue; else return new Tuple(false, null); } } return new Tuple(true, new List<int> { 0, 1, 2, 3, 4 }); }

The thing is when I am checking my "If" I get to the first method " RoyalFlushJokerHelper" and there I am deleting all my 5 items from flush list.

Then the problem is when i step into ContainAllItems method my flush list is empty.

I am not passing it by reference so why does the first method changes my original list ?

What makes you believe you do not pass it via reference ?

Paul Weiland
– Paul Weiland

2015-07-02 11:43:52 +00:00
Commented Jul 2, 2015 at 11:43 — Paul Weiland
– Paul Weiland, Commented Jul 2, 2015 at 11:43

Yeldar Kurmangaliyev · Accepted Answer · 2015-07-02 11:54:18Z

In C# only these objects are value-types:

Numeric data types
Boolean, Char, and Date
structs
enums
Long, Byte, UShort, UInteger, or ULong

All other objects are reference-types and when you pass them to a function, you pass it as reference.
If you want to change your List without affecting it, you can clone it before:

public bool RoyalFlushJokerHelper(object honoursOnTheScreen, List<Honours> honours) { var honoursCopy = honours.Clone(); // work with honoursCopy }

Please, read some information about values types and reference types.
For example, take a look at MSDN article "Value Types and Reference Types".

class objects are reference-type is not true because premitive type also derived from that type only. its parent of all type in .net
@PranayRana I didn't mean objects. I meant class objects - the objects which are classes. Probably, I named it wrong. Anyway, I have fixed an answer. Please, if you don't mind, review it and let me know if something's wrong.

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