Convert List
When dealing with inheritance, it is sometimes necessary to convert a list of derived class objects into a list of base class objects. However, this can lead to errors if not handled properly.
Error in list conversion using writable data
Consider the following code:
using System; using System.Collections.Generic; class Animal { public virtual void Play(List<Animal> animal) { } } class Cat : Animal { public override void Play(List<Animal> animal) { } } class Program { static void Main(string[] args) { Cat cat = new Cat(); cat.Play(new List<Cat>()); } }
This code will generate a compilation error due to a mismatch in the list object types. Animal expects a list of its own type (Animal), but this method is called with a list of Cat objects.
Error reason
This error occurs because the list is writable. If the conversion is allowed, it may cause data manipulation problems. For example, a dog object could be added to a list of cats, which would violate type safety.
Generic covariance
In C# 4, a feature called generic covariance was introduced. This allows a list of derived classes to be converted to a list of base classes, provided these types ensure type safety. An example of a safe type for generic covariance is IEnumerable<t></t>
, which represents a sequence of objects but cannot be written to.
Implementing generic covariance
To implement generic covariance, you can change the method signature in the base class to use IEnumerable<t></t>
as the parameter type, like this:
class Animal { public virtual void Play(IEnumerable<Animal> animals) { } } class Cat : Animal { public override void Play(IEnumerable<Animal> animals) { } } class Program { static void Main() { Cat cat = new Cat(); cat.Play(new List<Cat>()); } }
In this example, the Play method in Animal takes IEnumerable<animal></animal>
as a parameter, which allows it to accept a sequence of Animal and Cat objects.
The above is the detailed content of How Can I Safely Cast a List to List in C#?. For more information, please follow other related articles on the PHP Chinese website!

The future of C will focus on parallel computing, security, modularization and AI/machine learning: 1) Parallel computing will be enhanced through features such as coroutines; 2) Security will be improved through stricter type checking and memory management mechanisms; 3) Modulation will simplify code organization and compilation; 4) AI and machine learning will prompt C to adapt to new needs, such as numerical computing and GPU programming support.

C is still important in modern programming because of its efficient, flexible and powerful nature. 1)C supports object-oriented programming, suitable for system programming, game development and embedded systems. 2) Polymorphism is the highlight of C, allowing the call to derived class methods through base class pointers or references to enhance the flexibility and scalability of the code.

The performance differences between C# and C are mainly reflected in execution speed and resource management: 1) C usually performs better in numerical calculations and string operations because it is closer to hardware and has no additional overhead such as garbage collection; 2) C# is more concise in multi-threaded programming, but its performance is slightly inferior to C; 3) Which language to choose should be determined based on project requirements and team technology stack.

C isnotdying;it'sevolving.1)C remainsrelevantduetoitsversatilityandefficiencyinperformance-criticalapplications.2)Thelanguageiscontinuouslyupdated,withC 20introducingfeatureslikemodulesandcoroutinestoimproveusabilityandperformance.3)Despitechallen

C is widely used and important in the modern world. 1) In game development, C is widely used for its high performance and polymorphism, such as UnrealEngine and Unity. 2) In financial trading systems, C's low latency and high throughput make it the first choice, suitable for high-frequency trading and real-time data analysis.

There are four commonly used XML libraries in C: TinyXML-2, PugiXML, Xerces-C, and RapidXML. 1.TinyXML-2 is suitable for environments with limited resources, lightweight but limited functions. 2. PugiXML is fast and supports XPath query, suitable for complex XML structures. 3.Xerces-C is powerful, supports DOM and SAX resolution, and is suitable for complex processing. 4. RapidXML focuses on performance and parses extremely fast, but does not support XPath queries.

C interacts with XML through third-party libraries (such as TinyXML, Pugixml, Xerces-C). 1) Use the library to parse XML files and convert them into C-processable data structures. 2) When generating XML, convert the C data structure to XML format. 3) In practical applications, XML is often used for configuration files and data exchange to improve development efficiency.

The main differences between C# and C are syntax, performance and application scenarios. 1) The C# syntax is more concise, supports garbage collection, and is suitable for .NET framework development. 2) C has higher performance and requires manual memory management, which is often used in system programming and game development.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Dreamweaver CS6
Visual web development tools

SublimeText3 Chinese version
Chinese version, very easy to use

Notepad++7.3.1
Easy-to-use and free code editor

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.
