C#

[C#] Lambda Expressions

A lambda expression is an anonymous function that you can use to create delegates or expression tree types. By using lambda expressions, you can write local functions that can be passed as arguments or returned as the value of function calls. Lambda expressions are particularly helpful for writing LINQ query expressions.

To create a lambda expression, you specify input parameters (if any) on the left side of the lambda operator =>, and you put the expression or statement block on the other side. For example, the lambda expression x => x * x specifies a parameter that’s named x and returns the value of x squared. You can assign this expression to a delegate type, as the following example shows:

delegate int del(int i);  
static void Main(string[] args)  
{  
    del myDelegate = x => x * x;  
    int j = myDelegate(5); //j = 25  
}

To create an expression tree type:

using System.Linq.Expressions;  

namespace ConsoleApplication1  
{  
    class Program  
    {  
        static void Main(string[] args)  
        {  
            Expression<del> myET = x => x * x;  
        }  
    }  
}

Read more: https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/statements-expressions-operators/lambda-expressions

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C#

[C#]Generics

Generics refers to the technique of writing the code for a class without specifying the data type(s) that the class works on.

You specify the data type when you declare an instance of a generic class. This allows a generic class to be specialized for many different data types while only having to write the class once.

Example:

// Declare the generic class.
public class GenericList<T>
{
    void Add(T input) { }
}
class TestGenericList
{
    private class ExampleClass { }
    static void Main()
    {
        // Declare a list of type int.
        GenericList<int> list1 = new GenericList<int>();

        // Declare a list of type string.
        GenericList<string> list2 = new GenericList<string>();

        // Declare a list of type ExampleClass.
        GenericList<ExampleClass> list3 = new GenericList<ExampleClass>();
    }
}
  • Use generic types to maximize code reuse, type safety, and performance.

  • The most common use of generics is to create collection classes.

  • The .NET Framework class library contains several new generic collection classes in the System.Collections.Generic namespace. These should be used whenever possible instead of classes such as ArrayList in the System.Collections namespace.

  • You can create your own generic interfaces, classes, methods, events and delegates.

  • Generic classes may be constrained to enable access to methods on particular data types.

  • Information on the types that are used in a generic data type may be obtained at run-time by using reflection.