`SqlParameter Parameters.Add vs. AddWithValue: Which Method Should You Choose?`

Singleton pattern ensures that a class has only one instance and provides global access points. C 11 recommends using local static variables to implement thread-safe lazy loading singletons. 1. Use thread-safe initialization and delayed construction of static variables in the function; 2. Delete copy construction and assignment operations to prevent copying; 3. Privatization of constructs and destructors ensures that external cannot be created or destroyed directly; 4. Static variables are automatically destructed when the program exits, without manually managing resources. This writing method is concise and reliable, suitable for loggers, configuration management, database connection pooling and other scenarios. It is the preferred singleton implementation method under C 11 and above standards.

std::list is a two-way linked list container, suitable for scenarios where deleted elements are frequently inserted and deleted at any location but does not support random access. Its common operations include: 1. Insert elements using push_back, push_front, emplace_back, emplace_front; 2. Its traversal through three ways: scope for, forward iterator, and reverse iterator; 3. Delete elements using remove, pop_front, and pop_back; 4. Find the specified value with the help of the find algorithm; 5. Call sort member function to sort; 6. Sort first and then call unique to remove continuous repeat elements; 7. Use size and empty to query the container status, and the final output

static_cast can be used for basic data type conversion, such as double to int or int to char; 2. Support pointer up conversion (subclass → parent class) and cautious down conversion (parent class → child class); 3. Support reference type conversion, such as Derived reference to Base reference; 4. Allow safe conversion between void* and other pointer types, provided that the type is correct; 5. Recommend alternative C-style conversion to improve code clarity and security, but does not perform runtime type checks, const cannot be removed or used for independent type pointer conversion. static_cast is the preferred method of type-safe conversion in C, and is suitable for explicit and related types conversion.

In C, it is recommended to use find instead of count to determine whether the std::map key exists; 2. Find has higher performance and can directly obtain values to avoid repeated searches; 3. Count is only used to judge existence, but it is impossible to obtain values; 4. Count and operator[] should be avoided in combination to prevent secondary searches; 5. Only find or count can be used for constmap, and operator[] is not available; 6. Overall, find is preferred, taking into account efficiency and function, find is a better solution.

Figures are commonly represented by adjacency tables in C, which are suitable for modeling various relationships. 1. Use std::unordered_map to flexibly process any vertex tag, and support dynamic addition of nodes; 2. For vertices numbered from 0 to N-1, use std::vector is more efficient; 3. Undirected graphs need to add edges in both directions, and directed graphs only add one-way; 4. Printing an adjacency table can verify the graph structure; 5. Select data structure according to requirements: use vector to fix the number of vertices, use unordered_map to any label, and use unordered_set when it is necessary to quickly delete edges. This implementation lays the foundation for subsequent implementation of algorithms such as BFS, DFS and shortest paths.

This example shows basic TCP client-server communication implemented using C on Linux/Unix systems. 1. The server creates a socket and binds it to port 8080; 2. Start listening to connection requests; 3. Accept client connections; 4. Read messages sent by the client; 5. Send a response to the client; 6. Close the connection. The client executes: 1. Create sockets; 2. Connect to the server IP and port; 3. Send messages; 4. Receive server responses; 5. Close the connection. The program uses standard system calls, including error handling, and is suitable for local loopback testing, and is the basic implementation of introductory network programming.

The explicit constructor is a constructor declared using the explicit keyword, which prohibits the compiler from implicit type conversion. 1. For single-parameter constructors, when explicit is not added, the compiler will automatically implicitly convert the parameter type to class type, which may lead to unexpected behavior; 2. After using explicit, constructors such as MyString(5) or Point{3,4} must be called explicitly, and implicit conversions such as MyStrings=10 or printString(5) are prohibited; 3. Starting from C 11, explicit can be used for multi-parameter constructors to prevent implicit conversions of list initialization; 4. It is recommended to use explore in most constructors.

To write a file in C, you need to include the header file and use the ofstream object. 1. Create the ofstream object during basic writing and check is_open() to ensure that the file is opened successfully.