- .NET Framework (.NF) - an integral Windows component.
- Value types (VT) - simplest types in .NF.
- Contain their data directly - no ref to data stored elsewhere.
- Instances of VT stored on stack.
- 3 general VTs: built-in types, user-defined types, enumerations. Each is derived from System.ValueType.
Built-in VTs
- Base types, provided by .NF. Other types are built from these.
- Optimizing performance - runtime optimizes perf. of Int32 & UInt32. For F.P use Double.
- VTs function as objects - you can call methods on them (e.g. ToString() ).
- In .NT, all types are derived from System.Object.
Declaring VTs
- declare symbol as instance of that type.
- VTs - implicit constructor - declaring them instantiates the type automatically. (No ''new' keyword).
- Constructor assigns a default value to new instance (e.g. o or null).
- Best practice - explicitly initialize within declaration - bool b = false;
- C# is case-sensitive.
- Nullable - new type in .NF 2.0 - allows one to determine whether a value has been assigned or not.
- Nullable
b = null; - Shorthand - bool? b = null;
- HasValue and Value members - if (b.HasValue) ... else ...;
Creating User-Defined Types
- UDFs - structures/structs.
- structs - composite of other types - easier to work with related data.
- example - System.Drawing.Point.
- explicit construction - System.Drawing.Point p = new System.Drawing.Point(2,3);
- define own structures ~ struct keyword.
- Class/Struct - former created on heap & is ref type, latter created on stack & is VT.
Creating Enumerations
- Enums - related symbols that have fixed values.
- Use to provide a list of choices to developers using your class.
- E.g. - enum Titles : int { Mr, Ms, Mrs, Dr };
- Use when developers consuming your types must choose from a limited set of choices for a value.
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Structs
- struct - UDT. A lightweight class.
- similar - constructors, methds, fields, properties, operators,...
- diffs - dont support inheritance (cant inherit from any other class + implicitly sealed), or destructors. Class ref type, struct VT.
- structs - use only for types that are small, simple, and similar in behaviour and characteristics to built-in types.
- structs - > efficient in arrays, <>
- structs - can implement mult. interfaces.
- diffs - no custom default (i.e parameterless) constructor. Also cannot init. an instance fld in a struct (e.g. private int xVal = 50; )
- structs - can create without 'new' - though not recommended - more difficult to read.
- struct - override ToString() - prevents boxing. (e.g. when passing -> WriteLine() ).
