Whilst getting my head around Rob Conery’s Massive ORM, I needed to figure out what the dynamic keyword is in C#4:
class Program {
static void Main(string[] args) {
Calculator calc = new Calculator();
int sum = calc.Add(1, 2);
Console.WriteLine(sum);
Console.ReadLine();
}
}
public class Calculator {
public int Add(int a, int b) {
return a+b;
}
}
creation of an object, invokation of a method, and the collection of a return value
Var
Can represent any type that can be determined at compile time.
class Program {
static void Main(string[] args) {
//int
var i = 5;
//string
var x = "hello";
//int[]
var y = new[] { 0, 1, 2, 3 };
//anonymous type
var anon = new { Name = "Dave", Age = 34 };
//List<int>
var list = new List<int>();
//Calculator
var calc = new Calculator();
int sum = calc.Add(1, 2);
Console.WriteLine(sum);
Console.ReadLine();
}
}
public class Calculator {
public int Add(int a, int b) {
return a+b;
}
}
Dynamic
at runtime you get the type
class Program {
static void Main(string[] args) {
//int
dynamic i = 5;
//string
dynamic x = "hello";
//int[]
dynamic y = new[] { 0, 2, 3, 4 };
//anonymous type
dynamic anon = new {Name="Dave", Age=34};
Console.WriteLine(i + x);
dynamic calc = new Calculator();
//don't get intellisense when press .
int sum = calc.Add(1, 2);
Console.WriteLine(sum);
Console.ReadLine();
}
}
public class Calculator {
public int Add(int a, int b) {
return a+b;
}
}
ExpandoObject and TryInvokeMember
An object whose members can be dynamically added and removed at runtime.
can’t do anything with the expandoObject though!
Much better. Saying to the compiler – “Playing with a different set of rules”.
Why doesn’t Product need to by Dynamic?
dynamic tbl = new DynamicModel("Northwind", "Products", "ProductID");
//tbl.Single returns a dynamic of type ExpandoOnject, not an ExpandoObject.
//acutally an IEnumrable<dynamic>.FirstOfDefault()
var product = tbl.Single();
We don’t need product to be dynamic here as tbl.Single returns a dynamic of type Expando.
tbl has to be dynamic otherwise the TryInvokeMember wont work, as there is no method called Single.