First, let’s introduce the XMLHttpRequest object. We all know that Ajax is not just a single technology, but a fusion of several technologies. XMLHttpRequest is the core technology in the Ajax technology system. Without XMLHttpRequest, the other Ajax technologies cannot become an organic whole. In Ajax applications, the XMLHttpRequest object is responsible for sending user information to the server asynchronously and receiving response information and data returned by the server.
XMLHttpRequest is an object of the XMLHttp component. Using XMLHttpRequest can partially update web page information without submitting the entire page to the server. Maybe it’s a bit abstract. Everyone often goes to QQ space to see what their friends are doing. Some friends have shared videos. After we click play, the mouse and keyboard do not lose their mobility either during the video buffering or during playback. We can continue browsing. For other dynamics, when we slide the mouse wheel up and down, the video page also moves up and down following the current position we browse, as shown in the figure below. Such a function can be achieved through Ajax.
The XMLHttpRequest object provides a series of properties and methods to send asynchronous HTTP requests to the server. When the server processes user requests, the XMLHttpRequest object reflects the status of the HTTP request in real time through the status value of the attribute and guides JavaScript to perform corresponding processing based on the obtained status. In addition, when the server successfully responds to the user's action and returns the user, the response series methods provided by XMLHttpRequest can assemble the returned data into text format, XML format or unsigned
JavaScript script processing provided by byte data format.
Before using the XMLHttpRequest object to send requests and process responses, you must use javascript to create an XMLHttpRequest object. Since the XMLHttpRequest object is not yet a W3C standard, the creation methods are different in new versions of IE browsers, old versions of IE browsers, and non-IE browsers. Therefore, you need to determine the browser type before creating an XMLHttpRequest object. For IE browsers with lower versions, you need to use Microsoft.XMLHTTP, and for IE browsers with higher versions, you need to use Msxml2.XMLHTTP.
The following is the code to create the XMLHttpRequest object:
<span style="font-family:KaiTi_GB2312;font-size:18px;"> <script language="javascript" type="text/javascript"> var xmlHttp; //使用新版本的IE创建XMLHttpRequest对象 try { xmlHttp = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { //使用旧版本的IE创建XMLHttpRequest对象 try { xmlHttp = new ActiveXObject("Microsoft.XMLHTTP"); } catch (E) {} } //使用其他浏览器创建XMLHttpRequest对象 if (!xmlHttp && typeof XMLHttpRequest !='undefined') { try{ xmlHttp=new XMLHttpRequest(); } catch (e) { xmlHttp = false; } } </script></span>
From the code We can see that although logical judgment is required, creating an XMLHttpRequest object is not complicated. My understanding of XMLHttpRequest is not very thorough. I just compiled it based on the examples in the video and the knowledge in the Ajax programming technology textbook. I hope everyone can communicate more and make progress together.
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C# and .NET provide powerful features and an efficient development environment. 1) C# is a modern, object-oriented programming language that combines the power of C and the simplicity of Java. 2) The .NET framework is a platform for building and running applications, supporting multiple programming languages. 3) Classes and objects in C# are the core of object-oriented programming. Classes define data and behaviors, and objects are instances of classes. 4) The garbage collection mechanism of .NET automatically manages memory to simplify the work of developers. 5) C# and .NET provide powerful file operation functions, supporting synchronous and asynchronous programming. 6) Common errors can be solved through debugger, logging and exception handling. 7) Performance optimization and best practices include using StringBuild

.NETFramework is a cross-language, cross-platform development platform that provides a consistent programming model and a powerful runtime environment. 1) It consists of CLR and FCL, which manages memory and threads, and FCL provides pre-built functions. 2) Examples of usage include reading files and LINQ queries. 3) Common errors involve unhandled exceptions and memory leaks, and need to be resolved using debugging tools. 4) Performance optimization can be achieved through asynchronous programming and caching, and maintaining code readability and maintainability is the key.

Reasons for C#.NET to remain lasting attractive include its excellent performance, rich ecosystem, strong community support and cross-platform development capabilities. 1) Excellent performance and is suitable for enterprise-level application and game development; 2) The .NET framework provides a wide range of class libraries and tools to support a variety of development fields; 3) It has an active developer community and rich learning resources; 4) .NETCore realizes cross-platform development and expands application scenarios.

Design patterns in C#.NET include Singleton patterns and dependency injection. 1.Singleton mode ensures that there is only one instance of the class, which is suitable for scenarios where global access points are required, but attention should be paid to thread safety and abuse issues. 2. Dependency injection improves code flexibility and testability by injecting dependencies. It is often used for constructor injection, but it is necessary to avoid excessive use to increase complexity.

C#.NET is widely used in the modern world in the fields of game development, financial services, the Internet of Things and cloud computing. 1) In game development, use C# to program through the Unity engine. 2) In the field of financial services, C#.NET is used to develop high-performance trading systems and data analysis tools. 3) In terms of IoT and cloud computing, C#.NET provides support through Azure services to develop device control logic and data processing.

.NETFrameworkisWindows-centric,while.NETCore/5/6supportscross-platformdevelopment.1).NETFramework,since2002,isidealforWindowsapplicationsbutlimitedincross-platformcapabilities.2).NETCore,from2016,anditsevolutions(.NET5/6)offerbetterperformance,cross-

The C#.NET developer community provides rich resources and support, including: 1. Microsoft's official documents, 2. Community forums such as StackOverflow and Reddit, and 3. Open source projects on GitHub. These resources help developers improve their programming skills from basic learning to advanced applications.

The advantages of C#.NET include: 1) Language features, such as asynchronous programming simplifies development; 2) Performance and reliability, improving efficiency through JIT compilation and garbage collection mechanisms; 3) Cross-platform support, .NETCore expands application scenarios; 4) A wide range of practical applications, with outstanding performance from the Web to desktop and game development.


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