The reasons why constructors cannot be declared as virtual functions:
1. The so-called virtual function means that only one is executed in polymorphic situations. From the concept of inheritance, the parent class object is always constructed first, and then the subclass object can be used. If the constructor is set to a virtual function, then you have to explicitly call the constructor when constructing the constructor of the parent class. Another reason is to prevent errors from happening. Imagine if you accidentally override it in the subclass If you create a function that is the same as the parent class constructor, then your parent class constructor will be overwritten, that is, the construction of the parent class cannot be completed, and an error will occur. public
class B: public A{
public:
B( )
Derived class inheritance results in polymorphism. In the constructor of the derived class, the compiler will add the code to construct the base class. If the constructor of the base class uses parameters, the derived class must provide parameters for the base class in its constructor. , this is the reason, the reason is a bit convoluted, that is, if the constructor of the derived class must be exactly the same as the parent class, this is obviously unrealistic
Of course there are other explanations: 1. From the perspective of storage space, virtual functions Corresponds to a vtable, but this vtable is actually stored in the memory space of the object. The problem arises. If the constructor is virtual, it needs to be called through the vtable, but the object has not been instantiated, that is, there is no memory space, and the vtable cannot be found, so the constructor cannot be a virtual function.
2. From the perspective of usage, virtual functions are mainly used to enable overloaded functions to be called accordingly when the information is incomplete. The constructor itself is to initialize the instance, so using virtual functions has no instance meaning. The first instance is not initialized, so how can it be polymorphic? The function of a virtual function is that when it is called through a pointer or reference of the parent class, it can become the member function that calls the subclass. The constructor is automatically called when an object is created, and cannot be called through a pointer or reference from the parent class. Therefore, it is stipulated that the constructor cannot be a virtual function.
3. From an implementation point of view, the vtable is created after the constructor is called, so the constructor cannot be a virtual function. From a practical point of view, the real type of the object cannot be determined when the constructor is called (subclasses need to call The constructor of the parent class), and the constructor provides initialization and is only executed once during the object's lifetime. It is not a dynamic behavior of the object, and there is no need to become a virtual function.

C#.NET is still important because it provides powerful tools and libraries that support multiple application development. 1) C# combines .NET framework to make development efficient and convenient. 2) C#'s type safety and garbage collection mechanism enhance its advantages. 3) .NET provides a cross-platform running environment and rich APIs, improving development flexibility.

C#.NETisversatileforbothwebanddesktopdevelopment.1)Forweb,useASP.NETfordynamicapplications.2)Fordesktop,employWindowsFormsorWPFforrichinterfaces.3)UseXamarinforcross-platformdevelopment,enablingcodesharingacrossWindows,macOS,Linux,andmobiledevices.

C# and .NET adapt to the needs of emerging technologies through continuous updates and optimizations. 1) C# 9.0 and .NET5 introduce record type and performance optimization. 2) .NETCore enhances cloud native and containerized support. 3) ASP.NETCore integrates with modern web technologies. 4) ML.NET supports machine learning and artificial intelligence. 5) Asynchronous programming and best practices improve performance.

C#.NETissuitableforenterprise-levelapplicationswithintheMicrosoftecosystemduetoitsstrongtyping,richlibraries,androbustperformance.However,itmaynotbeidealforcross-platformdevelopmentorwhenrawspeediscritical,wherelanguageslikeRustorGomightbepreferable.

The programming process of C# in .NET includes the following steps: 1) writing C# code, 2) compiling into an intermediate language (IL), and 3) executing by the .NET runtime (CLR). The advantages of C# in .NET are its modern syntax, powerful type system and tight integration with the .NET framework, suitable for various development scenarios from desktop applications to web services.

C# is a modern, object-oriented programming language developed by Microsoft and as part of the .NET framework. 1.C# supports object-oriented programming (OOP), including encapsulation, inheritance and polymorphism. 2. Asynchronous programming in C# is implemented through async and await keywords to improve application responsiveness. 3. Use LINQ to process data collections concisely. 4. Common errors include null reference exceptions and index out-of-range exceptions. Debugging skills include using a debugger and exception handling. 5. Performance optimization includes using StringBuilder and avoiding unnecessary packing and unboxing.

Testing strategies for C#.NET applications include unit testing, integration testing, and end-to-end testing. 1. Unit testing ensures that the minimum unit of the code works independently, using the MSTest, NUnit or xUnit framework. 2. Integrated tests verify the functions of multiple units combined, commonly used simulated data and external services. 3. End-to-end testing simulates the user's complete operation process, and Selenium is usually used for automated testing.

Interview with C# senior developer requires mastering core knowledge such as asynchronous programming, LINQ, and internal working principles of .NET frameworks. 1. Asynchronous programming simplifies operations through async and await to improve application responsiveness. 2.LINQ operates data in SQL style and pay attention to performance. 3. The CLR of the NET framework manages memory, and garbage collection needs to be used with caution.


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