Problem with passing the value

Question

If I nullify the value in the case of collection in the called function,it is not affecting in the calling method.It is still having the original values..Why the value is not null in the calling function..?

Dipa Ahuja · Answer

good que.. i also want to know it now :)

Jaish Mathews · Answer

Hi What understood is that you are asking why ArrayList not null even after made it null in side another function. Actually it's null only but you are not storing that value and seems like it's not null. Look below code and concentrate on bolded lines where I stored the latest version after nullified. Here I am getting null private void Form1_Load(object sender EventArgs e) { ArrayList arr = new ArrayList(); arr.Add(1); arr = SomeMethod(arr); } public ArrayList SomeMethod(ArrayList arr) { arr = null; return arr; }

Dipankar Sana · Answer

Thanks..It helped.. But I just wanted to know why it was behaving like that when not adding ref.. ?

Dipa Ahuja · Answer

ArrayList arr = new ArrayList(); arr.Add(1); SomeMethod(ref arr); if (arr != null) { for (int z = 0; z { label1.Text = label1.Text +   + arr[z]; } } private ArrayList SomeMethod(ref ArrayList Arrs) { Arrs.Add(2); Arrs = null; return Arrs; }

Dipankar Sana · Answer

Ya that I know..But my query is why this is behaving like this..? Why the null value is not reflecting whereas modifications are getting reflected ??

Dipa Ahuja · Answer

you can use ref keyword to pass by reference . ths will reflect the original array see this example http://msdn.microsoft.com/en-us/library/s6938f28.aspx

Dipankar Sana · Answer

This is the scenario.. I have created one arraylist. ArrayList arr=new ArrayList(); Arr.Add(1); SomeMethod(Arr); Public ArrayList SomeMethod(ArrayList Arrs) { Arrs.Add(2); return Arrs; } In the above case the updated result is getting reflected in the variable Arr in calling method i.e now we are getting two items in Arr. But if in SomeMethod function we nullify Arrs and return Arrs.its not getting updated with null value in calling function .Still it is having old value..i.e 1.

Dipa Ahuja · Answer

are you calling by value or reference? read the content about call by value and call by reference if its called by value then it doesnt affect the original value..