optional-parameters

I was watching Anders' talk about C# 4.0 and sneak preview of C# 5.0 , and it got me thinking about when optional parameters are available in C# what is going to be the recommended way to declare methods that do not need all parameters specified? For example something like the FileStream class has about fifteen different constructors which can be divided into logical 'families' e.g. the ones below from a string, the ones from an IntPtr and the ones from a SafeFileHandle . FileStream(string,FileMode); FileStream(string,FileMode,FileAccess); FileStream(string,FileMode,FileAccess,FileShare);

How do I deal with optional struct arguments in dll methods called from C# using pinvoke? For example, the lpSecurityAttributes parameter here should be passed null when absent. The correct way of passing struct 's seems to be using ref , but it cannot have optional parameters, or take null in general. What ways are there to achieve this? You have a few options 1) Use a class instead of a struct I think this method is the easiest. Simply declare the struct as a class : [StructLayout(LayoutKind.Sequential)] public class CStruct { //member-list } and then declare your method: [DllImport("mydll

1. int Add (int a, int b = 3); int Add (int a, int b) { } 2. int Add (int a, int b); int Add (int a, int b = 3) { } Both work; which is the standard way and why ? If you put the declaration in a header file, and the definition in a separate .cpp file, and #include the header from a different .cpp file, you will be able to see the difference. Specifically, suppose: lib.h int Add(int a, int b); lib.cpp int Add(int a, int b = 3) { ... } test.cpp #include "lib.h" int main() { Add(4); } The compilation of test.cpp will not see the default parameter declaration, and will fail with an error. For this

This question already has an answer here: Setting the default value of a C# Optional Parameter 3 answers How does one define a function that takes an optional array with an empty array as default? public void DoSomething(int index, ushort[] array = new ushort[] {}, bool thirdParam = true) results in: Default parameter value for 'array' must be a compile-time constant. You can't create compile-time constants of object references. The only valid compile-time constant you can use is null , so change your code to this: public void DoSomething(int index, ushort[] array = null, bool thirdParam =