calculator calc = getcalculator(); int sum = calc.add(10, 20); calculator calc = getcalculator();...
TRANSCRIPT
Dynamic Binding in C# 4.0
Mads TorgersenC# Language PMMicrosoft Corporation
FT31
Dynamic in C#
> The Dynamic Language Runtime (DLR)
> dynamic in C#
> Designing dynamic
The DLR on the CLR
> Common Language Runtime – CLR:> Common platform for static languages> Facilitates great interop
The DLR on the CLR
> Common Language Runtime – CLR:> Common platform for static languages> Facilitates great interop
> Dynamic Language Runtime – DLR:> Common platform for dynamic languages> Facilitates great interop
The DLR on the CLR
> Common Language Runtime – CLR:> Common platform for static languages> Facilitates great interop
> Dynamic Language Runtime – DLR:> Common platform for dynamic languages> Facilitates great interop
Dynamic Objects
> Implement their own binding
> The DLR caches and optimizes
> Built by dynamic languages – or you!
Why Dynamic in C#?
> Build on DLR opportunity
> Use code from dynamic languages
> Use other dynamic object models
> Better COM interop
The Dynamic Type in C#
Calculator calc = GetCalculator();int sum = calc.Add(10, 20);
object calc = GetCalculator();Type calcType = calc.GetType();object res = calcType.InvokeMember("Add", BindingFlags.InvokeMethod, null, new object[] { 10, 20 });int sum = Convert.ToInt32(res);
ScriptObject calc = GetCalculator();object res = calc.Invoke("Add", 10, 20);int sum = Convert.ToInt32(res);
dynamic calc = GetCalculator();int sum = calc.Add(10, 20);
Statically typed to be dynamic
Dynamic method
invocation
Dynamic conversion
C# Dynamic
demo
Designing Dynamic
> C# is not a dynamic language!
> Dynamic is a dangerous foreign element
> Should be syntactically explicit
Static Example
string[] strings = GetStrings();
string last = strings[strings.Length – 1];
Explicit Dynamic Operations
object strings = GetDynamicObject();
string last = strings[strings.Length – 1];
Explicit Dynamic Operations
object strings = GetDynamicObject();
string last = strings[strings~.Length – 1];
Explicit Dynamic Operations
object strings = GetDynamicObject();
string last = strings~[strings~.Length – 1];
Explicit Dynamic Operations
object strings = GetDynamicObject();
string last = strings~[strings~.Length ~– 1];
Explicit Dynamic Operations
object strings = GetDynamicObject();
string last = (string)strings~[strings~.Length ~– 1];
Explicit Dynamic Operations
object strings = GetDynamicObject();
string last = ~(string)strings~[strings~.Length ~– 1];
Explicit Dynamic Operations
> Reads horribly!
> Dynamic binding travels in packs!
object strings = GetDynamicObject();
string last = ~(string)strings~[strings~.Length ~– 1];
Explicit Dynamic Operations
> Reads horribly!
> Dynamic binding travels in packs!
object strings = GetDynamicObject();
string last = ~(string)strings~[strings~.Length ~– 1];
Dynamic Contexts
object strings = GetDynamicObject();string last; dynamic { last = strings[strings.Length – 1]; }
Dynamic Contexts
object strings = GetDynamicObject();string last; dynamic { last = strings[strings.Length – 1]; }
> Different dialect of C# inside> Opt out with static contexts?> Lose sight of big contexts
Dynamic Contexts
> Different dialect of C# inside> Opt out with static contexts?> Lose sight of big contexts
object strings = GetDynamicObject();string last; dynamic { last = strings[strings.Length – 1]; }
Contagious Dynamic Expressions
object strings = GetDynamicObject(); string last = strings[dynamic(strings).Length – 1];
Contagious Dynamic Expressions
> Rules of propagation – what is dynamic?
> Factoring out subexpressions is hard
object strings = GetDynamicObject(); string last = strings[dynamic(strings).Length – 1];
Contagious Dynamic Expressions
> Rules of propagation – what is dynamic?
> Factoring out subexpressions is hard
object strings = GetDynamicObject(); string last = strings[dynamic(strings).Length – 1];
Dynamic Type
dynamic strings = GetDynamicObject(); string last = strings[strings.Length – 1];
Dynamic Type
> “Dynamicness” follows the object
> There is no syntactic difference!
dynamic strings = GetDynamicObject(); string last = strings[strings.Length – 1];
Dynamic Type
> “Dynamicness” follows the object
> There is no syntactic difference!
dynamic strings = GetDynamicObject(); string last = strings[strings.Length – 1];
Why is this OK?
> Embrace dynamic!
> Still explicit – just not in syntax!
> Replaces lengthy error-prone code
Type or Type Modifier?
> Generality:
> Static binding of Foo’s members> Dynamic binding of the rest
> Simplicity:
> Dynamic binding of all members> Even those on Object
dynamic Foo foo = GetDynamicFoo();
dynamic foo = GetDynamicFoo();
Type or Type Modifier?
> Generality:
> Static binding of Foo’s members> Dynamic binding of the rest
> Simplicity:
> Dynamic binding of all members> Even those on Object
dynamic Foo foo = GetDynamicFoo();
dynamic foo = GetDynamicFoo();
Dynamic Binding When?
> When the receiver is dynamic:
> Forces you to choose a type
> When any subexpression is dynamic:
> Softer landing
dynamic result = Math.Abs((double)d);
dynamic result = Math.Abs(d);
Dynamic Binding When?
> When the receiver is dynamic:
> Forces you to choose a type
> When any subexpression is dynamic:
> Softer landing
dynamic result = Math.Abs((double)d);
dynamic result = Math.Abs(d);
Dynamic Operations
> Dynamic result:> Method call Math.Abs(d)> Invocation d(“Hello”)> Member access d.Length> Operator application 4 + d> Indexing d[“Hello”]
> Static result:> Conversions (double)d> Object creation new Foo(d)
M(GetFoo(), d);
How Dynamic?
Bind with compile-time
type
Bind with runtime type
M(GetFoo(), d);
How Dynamic?
> “Just enough” dynamicness
> Principle of least surprise:> Argument’s contribution to binding is
invariant
Bind with compile-time
type
Bind with runtime type
The Meaning of dynamic
dynamic means“use my runtime type for binding”
Twice Daily Against Skepticism
> Which would you rather see – or write?
Type calcType = calc.GetType();object res = calcType.InvokeMember("Add", BindingFlags.InvokeMethod, null, new object[] { 10, 20 });int sum = Convert.ToInt32(res);
int sum = calc.Add(10, 20);
or
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Using Dynamic Languages to Build Scriptable ApplicationsNovember 17, 12:30 - 13:15 – 403AB Dino Viehland
Dynamic Binding in C# 4 November 17, 12:30 - 13:15 – Hall F Mads Torgersen
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