Is there a C3 equivalent to the VB "Preserve" keyword?

Question

In other words, how can you dynamically resize an array without losing its values?

joy.simpson · Answer

Thanks for the info. I'm teaching a combined course in VB.NET and C# and trying to create demo programs for my students that show code for the 2 languages side-by-side with the identical output. Guess I'll just have to tell them that the technique for preserving resized array values in C# is the same as the one we used in QBasic!

ssswamii · Answer

There isn't a way to dynamically resize a value array in C#. However, you have 2 options right now, and you'll have another option come early 2003. First option is to use the System.Collections.ArrayList class which will automatically grow as more elements are added to it. It's nice, but everything added gets casted to System.Object and every time you retrieve an item, it gets returned as System.Object. This isn't a serious problem for reference types (such as class references and the like), but for value types like ints and floats, an operation gets done in the background known as "boxing" when you put a value in, and unboxing when you take a value out. Boxing and unboxing cause a lot of overhead and will hurt performance. Your other option would be to just recreate array when it needs to grow. myPreviouslyCreatedArray = new int[moreElements]; // fill it... Recreating the array is a ~very~ fast operation - I did a test in C# where I created an a large int array and filled it with many ints and I didn't even notice a pause. It wasn't until I got up to about a 10,000,000 int array before I even noticed a momentary pause on my P4 machine. Finally, in the next release of the Whidbey CLR and C# 2.0, C# will have support for the creation and consumption of generics, plus some generic classes built-in to the framework. Using generics, you will be able to create an generic array list that doesn't incure boxing overhead. It would look like // create a new array list that will store only ints System.Collections.Generic.ArrayList myGenericList = new ArrayList (); myGenericList.Add(5); ... Your best bet is generics when they are released early next year; they're fast, reuseable, and type safe. Until then, I'd just recreate the array yourself when you need to grow it. I'm not 100% sure, but I think VB might just being doing that under the hood when you ReDim it anyway.

vipin.sasi · Answer

hi, i think therez no equivalent!

david 0 · Answer

The Array Class supports dynamically sized arrays.

Is there a C3 equivalent to the VB "Preserve" keyword?

Answers (4)