Question

I know this sounded stupid. But I gotta be doing something wrong here.

Say,

struct lala {     private bool state1;      public lala(bool state1)     {         this.state1 = state1;     }      public void SetState1ToTrue()     {         this.state1 = true;     }      public bool GetState1()     {         return this.state1;     } } 

Then somewhere…

List<lala> lalas = new List<lala>();  lalas.Add(new lala(false)); lalas.Add(new lala(false));  lalas[0].SetState1ToTrue();  // Why is it False??? Console.WriteLine(lalas[0].GetState1()); 

Are there any workarounds to this except changing it to:

List<lala> lalas = new List<lala>();  lalas.Add(new lala(false)); lalas.Add(new lala(false));  lala newLala = lalas[0]; newLala.SetState1ToTrue(); lalas[0] = newLala;  // It's True, finally. Console.WriteLine(lalas[0].GetState1()); 

Which looked awful, unelegant and wasted 2 lines of code. If there’s any Linq-ish or Functional Programming-ish way in say 1 line of code that would be awesome.

Answer 1

The problem is in this line:

lalas[0].SetState1ToTrue(); 

The first part, lalas[0], retrieves the first lala from the list, and does so as a new copy of it in an implicit variable. So your SetState1ToTrue operates on a lala that is then immediately discarded, and the one in the list remains the same. It’s the same as doing this:

lala newLala = lalas[0]; newLala.SetState1ToTrue(); 

If you make lala a class not a struct, so that it becomes a reference type, then the temporary variable (explicit or implicit) is a reference to the lala within the list.