TheyieldkeywordinC#simplifiesiteratorcreationbyautomaticallygeneratingastatemachinethatenableslazyevaluation.1.Itallowsreturningitemsoneatatimeusingyieldreturn,pausingexecutionbetweeneachitem,whichisidealforlargeordynamicsequences.2.yieldbreakcanbeus

DependencyInjection(DI)inC#isadesignpatternthatenhancesmodularity,testability,andmaintainabilitybyallowingclassestoreceivedependenciesexternally.1.DIpromotesloosecouplingbydecouplingobjectcreationfromusage.2.Itsimplifiestestingthroughmockobjectinject

The role of IDisposable and using in C# is to efficiently and deterministically manage unmanaged resources. 1. IDisposable provides Dispose() method, so that the class can clearly define how to release unmanaged resources; 2. The using statement ensures that Dispose() is automatically called when the object is out of scope, simplifying resource management and avoiding leakage; 3. When using it, please note that the object must implement IDisposable, can declare multiple objects, and should always use using for types such as StreamReader; 4. Common best practices include not relying on destructors to clean up, correctly handling nested objects, and implementing the Dispose(bool) pattern.

LambdaexpressionsandLINQsimplifydatamanipulationinC#byenablingconcise,readable,andefficientcode.1.Lambdaexpressionsallowinlinefunctiondefinitions,makingiteasiertopasslogicasargumentsforfiltering,transforming,sorting,andaggregatingdatadirectlywithinme

Span and Memory improve C# performance by reducing memory allocation. 1. Span avoids array copying and provides light references to existing memory, which is suitable for parsing binary protocols, string operations and high-performance buffer management; 2. Memory supports passing memory slices across asynchronous methods, which is suitable for scenarios where more flexible life cycles are required; 3. Both reduce GC pressure, optimize performance by reusing buffers and avoiding temporary copying; 4. Span is limited to use on the stack and cannot be stored in classes or used in asynchronous methods. Be careful to avoid reassignment operations such as calling.ToArray().

Nullablereferencetypes(NRTs)inC#8 helpcatchNullReferenceExceptionerrorsatcompiletimebymakingreferencetypesnon-nullablebydefault,requiringexplicitdeclarationfornullability.NRTsmustbeenabledeitherinthe.csprojfilewithenableoratthetopofa.csfileusing#null

Four common "anti-pattern" problems in C# development need to be avoided. First, the unreasonable use of async/await leads to deadlocks or performance degradation. We should adhere to the principle of full asynchronousness, configure ConfigureAwait(false) and standardize naming; second, excessive dependence on var affects readability, and explicitly declare and unify team specifications when the type is unclear; third, the incorrect use of Dispose and resource management causes leakage, and the use statement should be used correctly and the IDisposable standard mode should be implemented; fourth, the abuse of static classes or singletons causes testing difficulties, and priority should be given to dependency injection, statelessness, or the life cycle managed by containers. Avoiding these misunderstandings can significantly improve code quality and maintenance.

SOLID principle is five design principles to improve code maintainability and scalability in object-oriented programming. They are: 1. The single responsibility principle (SRP) requires that the class only assumes one responsibility, such as separating report generation and email sending; 2. The opening and closing principle (OCP) emphasizes that the extension is supported through interfaces or abstract classes without modifying the original code, such as using the IShape interface to realize area calculation of different graphics; 3. The Richter replacement principle (LSP) requires that the subclass can replace the parent class without destroying logic, such as Square should not mistakenly inherit Rectangle, resulting in abnormal behavior; 4. The interface isolation principle (ISP) advocates the definition of fine-grained interfaces, such as split printing and scanning functions to avoid redundant dependencies; 5. The dependency inversion principle (DIP) advocates the