How to connect to a SQL Server database in C#?

C#'s TPL simplifies parallel task processing through the Task class. 1. Use Task.Run() or Task.Factory.StartNew() to start the task, and recommend the former; 2. Get the result through Task and wait for completion with await or .Result; 3. Use Task.WhenAll() to execute multiple tasks in parallel, pay attention to resource competition; 4. Use AggregateException to handle exceptions, and traverse specific errors after catching; 5. Use CancellationTokenSource to cancel the task, which is suitable for timeout or user cancellation scenarios; at the same time, pay attention to avoid mixing synchronous and asynchronous code to prevent deadlock problems.

When using var, it should be determined based on whether the type is clear and whether the readability is affected. 1. When the type is clear on the right side of the assignment, such as varlist=newList(); can improve the code simplicity; 2. When the type is fuzzy or returns to object or interface type, var should be avoided, such as IEnumerableresult=SomeMethod(); to improve readability; 3. Use var reasonably in anonymous types and LINQ queries, such as receiving anonymous objects, but subsequent processing is recommended to encapsulate it as a specific type; 4. In team projects, coding style should be unified, and var should be used reasonably through .editorconfig or code review to avoid abuse and affect maintenance.

Comparing strings in C# should be based on the scene selection method. The == operator is case-sensitive by default and compared based on the current culture, but is not suitable for complex scenarios. 1. Using the == operator is suitable for quick comparison, but may not meet the expected results due to culture or case; 2. Using String.Equals() and passing in StringComparison enumeration can achieve more precise control, such as Ordinal, OrdinalIgnoreCase, InvariantCulture, etc.; 3. Pay attention to handling null or empty strings when comparing. It is recommended to use the string.Equals() static method or use string.IsNullOrEmpt first.

To connect to a SQLServer database, the most common way to C# is to use the SqlConnection class in ADO.NET. 1. You need to install the Microsoft.Data.SqlClient package and reference the namespace; 2. Write a connection string containing the server address, database name, and authentication information; 3. Use using and try-catch to establish a connection and execute queries, while ensuring resource release and exception handling; 4. Common problems include remote connection settings, firewall configuration, port release and login permissions, etc., and need to be checked one by one.

There are two common ways to read text files line by line in C#: using StreamReader and File.ReadLines(). 1. The ReadLine() method of StreamReader is suitable for processing large files, read line by line through loop and is memory friendly, and uses using to ensure resource release; 2. File.ReadLines() provides concise code, suitable for scenarios that only need to be traversed once, supports lazy loading and can specify encoding. If you need to access the file content multiple times, File.ReadAllLines() is recommended. The two automatically recognize encoding by default, but to avoid garbled code, it is recommended to explicitly specify Encoding.UTF8 and Enc as needed.

C#canbeusedforscientificcomputinganddataanalysisbysettingupaproperenvironment,leveragingrelevantlibraries,andoptimizingperformance.First,installVisualStudioorVSCodewiththe.NETSDKasthefoundation.Next,useNuGetpackageslikeMath.NETNumericsforlinearalgebr

Choosing the right collection type can significantly improve C# program performance. 1. Frequently insert or delete the LinkedList in the middle, 2. Quickly search using HashSet or Dictionary, 3. Fixed element count to use arrays first, 4. Select HashSet when unique values are required, 5. Frequently searching using Dictionary or SortedDictionary, 6. Consider ConcurrentBag or ConcurrentDictionary in multi-threaded environment.

In C#, the static keyword is used to define members belonging to the type itself and can be accessed without instantiation. 1. Static variables are shared by all instances of the class and are suitable for tracking global state, such as recording the number of instantiation of the class; 2. Static methods belong to classes rather than objects, and cannot directly access non-static members, and are often used in helper functions in tool classes; 3. Static classes cannot be instantiated and only contain static members. They are suitable for organizing stateless practical methods, but cannot inherit or implement interfaces. When using it, you need to pay attention to memory management and thread safety issues.