C#/.NET

1. C#/.NET Jacob Lewallen

2. C# vs .NET • .NET is a platform. • Many languages compile to .NET: • VB.NET • Python.NET • Managed C++ • C#

3. .NET • Intermediate Language (IL) – “half-way” • Interpreted locally using JIT (Just-In-Time) compilers. • Has a very nice standard library, comparable to Java’s. • Theme: More “open” to it’s hosted system than Java.

4. C# Basics • Garbage Collected • Very Java-esque: • Main is static method in some class • Designed for .NET, rather than adapted. • Simple operator overloading • Everything is an Object • Java-like inheritance

5. Safe vs Managed • Unmanaged – native code - non-IL code. • Unsafe code – code wrapped in C#’s unsafe mechanism: • Relaxed type checking • Pointers • Flagged as unsafe and requires more trust. • Unsafe code is still managed code.

6. Syntax • Think Java, if that fails think C++ public class ExampleApp { public static void Main() { string str = “Hello, World”; Console.WriteLine(str);} }

7. Namespaces • More like C++ namespaces, with some Java packages sprinkled in. using System.Collections; • Instead of using… System.Collections.Hashtable • Assemblies (DLLs) are named for the namespaces they contain, usually.

8. Declaring a Namespace • You can wrap your code in the namespace like so: Namespace UCR.Technical.Seminar { … } • Nearly all code I’ve ever seen has been wrapped in a Namespace.

9. Collections • System.Collections.Hashtable • System.Collections.ArrayList • Type-safe enumerations: foreach (string name in users) { … } • .NET will do runtime type checking.

10. Memory • All allocated memory is garbage collected. • We use new to create object instances. • We can override a finalizer for our classes to handle cleanup.

11. Value Types • Categories: Struct, Enumeration, Numeric Types (integers, floats, bools) • Assignments create copies of the assigned value. • Value types cannot contain null. • int is an alias for System.Int32, all value types have an alias.

12. Reference Types • Also referred to as object’s. • Store references to actual data. • Passed by reference, by default.

13. Boxing • Boxing - conversion from a value type to type object. It’s implicit: int x = 23; object o = 23; object r = x; • x is an integer on the heap, value is 23. • o is an object, referencing a new value on the heap, that’s 23. • r is an object, referencing the value x.

14. Unboxing • Explicit conversion from a reference type, an object, to a value type. object o = 23; int x = (int)o; • Type checking is done in the conversion. • Can throw InvalidCastException’s.

15. Properties • Replaces getter/setter paradigm. • Wraps private member variables around more defined accessors. • object.getName() you do object.Name. • object.setName(“Jacob”) becomes object.Name = “Jacob”; • Standard library uses upper case names for all properties.

16. Properties • Syntax for declaring a Property: String Name { get { return (m_name); } set { m_name = value; } } • Where m_name is our member variable. • Read-only Properties have no set.

17. Events/Delegates • Calling/invoking methods w/o knowing anything about the method’s object. • Defining a Delegate: public delegate void ButtonDelegate(string name); • This delegate takes a string and returns nothing.

18. Defining a Delegate • Declare a variable for out delegate: private ButtonDelegate m_presses; • We can create an instance of her: m_presses = new ButtonDelegate(SayHello); public bool SayHello(string name) { … } • Now, we can invoke/trigger the delegate: m_presses(“Hello, World”);

19. Using Delegates • Delegates are used exclusively for event handling in .NET GUI’s. • Many design patterns (publisher/subscribe)

20. Microsoft Whining • You can download the .NET SDK from Microsoft. You’ll get: • All the necessary command line utilities for developing with C#. • A few graphical tools for inspecting IL. • Help via http://msdn.microsoft.com/ • Visual Studio is NOT required.

21. Mono • Open Source .NET/C# implementation • http://www.go-mono.com/

22. Assembly • Think shared-object - *.dll or *.so.

23. ADO.NET

24. System.XML