Examples of usage of Generics in .Net (C#/VB.NET) [closed]

Question

What are some examples of where you would use generics in C#/VB.NET and why would you want to use generics?

Answer 1

Simply, you declare a type or method with extra tags to indicate the generic bits:

class Foo<T> {     public Foo(T value) {         Value = value;     }     public T Value {get;private set;} } 

The above defines a generic type Foo "of T", where the T is provided by the caller. By convention, generic type arguments start with T. If there is only one, T is fine - otherwise name them all usefully: TSource, TValue, TListType etc

Unlike C++ templates, .NET generics are provided by the runtime (not compiler tricks). For example:

Foo<int> foo = new Foo<int>(27); 

All Ts have been replaced with int in the above. If necessary, you can restrict generic arguments with constraints:

class Foo<T> where T : struct {} 

Now Foo<string> will refuse to compile - as string is not a struct (value-type). Valid constraints are:

T : class // reference-type (class/interface/delegate) T : struct // value-type except Nullable<T> T : new() // has a public parameterless constructor T : SomeClass // is SomeClass or inherited from SomeClass T : ISomeInterface // implements ISomeInterface 

Constraints can also involve other generic type arguments, for example:

T : IComparable<T> // or another type argument 

You can have as many generic arguments as you need:

public struct KeyValuePair<TKey,TValue> {...} 

Other things to note:

• static members etc are defined per generic type combination - so a static field on Foo<int> is separate to that on Foo<float>.
• methods can be generic too - try to avoid using the same names as the class uses, as you won't be able to disambiguate
• nested types inherit the generic types from their parents

for example:

class Foo<T> {     class Bar<TInner> {} // is effectively Bar<T,TInner>, for the outer T } 

Answer 2

Example 1: You want to create triple class

Class Triple<T1, T2, T3> {    T1 _first;    T2 _second;    T3 _Third; } 

Example 2: A helper class that will parse any enum value for given data type

static public class EnumHelper<T> {    static public T Parse(string value)    {        return (T)Enum.Parse(typeof(T), value);    } }