Comments from July Cleveland C# Sig

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Last night, I attended the local C# SIG.  I make sure I attend this SIG on a monthly basis.  The topic was on the new features C# 2010.  Here are my notes.

static dynamic type

• bypass type checking
• offload until runtime
• implicit conversion
• Examples
  • dynamic d = 7; // implicit conversion
  • int i = d;  // Since d is int, we can assign it to an integer
  • d = "Hello world"   // Now, d is a string
  • int i = d;  // this will not work (cannot place a string in int)
• Can take on type of object, which means that d can call methods from an object such as: 
  • dynamic d = o1.m()
  • but, this means that we can reassign d to another object that happens to have the same method name.  On a personal note, I can see this leading to bad code.  See this example:
    • dynamic d = obj;
    • d.method();
    • dynamic d = obj1;
    • d.method();  
• This was feature was because of the inclusion of F# and IronRuby in the Microsoft tool kit.
• yhere was a discussion if datatypes are tied to memory space or method space.  It was decided that datatypes are tied to method space unless they are declared as public.

covariance/contravariant

• converting specific to generic (string to object)
• utilize out keyword
• enable implicit reference conversion for array, delegates, interfaces (generic type argument)
• These are mostly used for generic interfaces

contravariant

• converting generic to specific (ex: generic to string)
• utilize in keyword

optional parameters

• lead to named parameters
• public void M(int x, int y=5, int z=7, int ii); // ii is the optional parameter
• M(1,Z:3);
• optional parameters after required arguments

COM Interop

• PIA:.Net assembly generated from COM interface
• No PIA deployment at runtime
• Compiler will incorporate necessary features into assembly
• ByRef implicitly defined

Call Hierarchy

• enables tp explore all possible execution paths
• shows 'Calls To'
• shows 'Call From'

• from generic to specific

Tuples

• fixed-size collection of different typed data. 
• strong typing for each element
• System.Tuple
• var BigTuple = Tuple.Create("Value",1,2,3,5.7, "Test",7)
• var Element1 = BigTuple.Item1;
• Tuple<string, int> t = new Tuple<string, int>("Hello", 4)
• string s = t.item1;
• int i = t.item2;