The example of this article describes the C# method of downloading the HTML source code of a web page. Share it with everyone for your reference. The specific method is as follows:
public static class DownLoad_HTML { private static int FailCount = 0; //记录下载失败的次数 public static string GetHtml(string url) //传入要下载的网址 { string str = string.Empty; try { System.Net.WebRequest request = System.Net.WebRequest.Create(url); request.Timeout = 10000; //下载超时时间 request.Headers.Set("Pragma", "no-cache"); System.Net.WebResponse response = request.GetResponse(); System.IO.Stream streamReceive = response.GetResponseStream(); Encoding encoding = Encoding.GetEncoding("gb2312");//utf-8 网页文字编码 System.IO.StreamReader streamReader = new System.IO.StreamReader(streamReceive, encoding); str = streamReader.ReadToEnd(); streamReader.Close(); } catch (Exception ex) { FailCount++; if (FailCount > 5) { var result = System.Windows.Forms.MessageBox.Show("已下载失败" + FailCount + "次,是否要继续尝试?" + Environment.NewLine + ex.ToString(), "数据下载异常", System.Windows.Forms.MessageBoxButtons.YesNo, System.Windows.Forms.MessageBoxIcon.Error); if (result == System.Windows.Forms.DialogResult.Yes) { str = GetHtml(url); } else { System.Windows.Forms.MessageBox.Show("下载HTML失败" + Environment.NewLine + ex.ToString(), "下载HTML失败", System.Windows.Forms.MessageBoxButtons.OK, System.Windows.Forms.MessageBoxIcon.Error); throw ex; } } else { str = GetHtml(url); } } FailCount = 0; //如果能执行到这一步就表示下载终于成功了 return str; }
I hope this article will be helpful to everyone’s C# programming
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The char array stores character sequences in C language and is declared as char array_name[size]. The access element is passed through the subscript operator, and the element ends with the null terminator '\0', which represents the end point of the string. The C language provides a variety of string manipulation functions, such as strlen(), strcpy(), strcat() and strcmp().

The core concepts of .NET asynchronous programming, LINQ and EFCore are: 1. Asynchronous programming improves application responsiveness through async and await; 2. LINQ simplifies data query through unified syntax; 3. EFCore simplifies database operations through ORM.

The usage methods of symbols in C language cover arithmetic, assignment, conditions, logic, bit operators, etc. Arithmetic operators are used for basic mathematical operations, assignment operators are used for assignment and addition, subtraction, multiplication and division assignment, condition operators are used for different operations according to conditions, logical operators are used for logical operations, bit operators are used for bit-level operations, and special constants are used to represent null pointers, end-of-file markers, and non-numeric values.

In C, the char type is used in strings: 1. Store a single character; 2. Use an array to represent a string and end with a null terminator; 3. Operate through a string operation function; 4. Read or output a string from the keyboard.

A strategy to avoid errors caused by default in C switch statements: use enums instead of constants, limiting the value of the case statement to a valid member of the enum. Use fallthrough in the last case statement to let the program continue to execute the following code. For switch statements without fallthrough, always add a default statement for error handling or provide default behavior.

In C language, special characters are processed through escape sequences, such as: \n represents line breaks. \t means tab character. Use escape sequences or character constants to represent special characters, such as char c = '\n'. Note that the backslash needs to be escaped twice. Different platforms and compilers may have different escape sequences, please consult the documentation.

There is no built-in sum function in C language, so it needs to be written by yourself. Sum can be achieved by traversing the array and accumulating elements: Loop version: Sum is calculated using for loop and array length. Pointer version: Use pointers to point to array elements, and efficient summing is achieved through self-increment pointers. Dynamically allocate array version: Dynamically allocate arrays and manage memory yourself, ensuring that allocated memory is freed to prevent memory leaks.

In C language, char type conversion can be directly converted to another type by: casting: using casting characters. Automatic type conversion: When one type of data can accommodate another type of value, the compiler automatically converts it.


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