鏈接示例：
<img src="https://thumbs.com/thumbs/test.mp4/test1.mp4-3.jpg" alt="This is the description i want to get too" >
以及我用來決議來自 html 下載的源檔案的鏈接的方法：
public List<string> GetLinks(string message)
{
List<string> list = new List<string>();
string txt = message;
foreach (Match item in Regex.Matches(txt, @"(http|ftp|https):\/\/([\w\-_] (?:(?:\.[\w\-_] ) ))([\w\-\.,@?^=%&:/~\ #]*[\w\-\@?^=%&/~\ #])?"))
{
if (item.Value.Contains("thumbs"))
{
int index1 = item.Value.IndexOf("mp4");
string news = ReplaceLastOccurrence(item.Value, "thumbs", "videos");
if (index1 != -1)
{
string result = news.Substring(0, index1 3);
if (!list.Contains(result))
{
list.Add(result);
}
}
}
}
return list;
}
但這只會給出我想獲得的鏈接，也給出這個例子中的鏈接描述：
這是一個測驗
然后使用它：
string[] files = Directory.GetFiles(@"D:\Videos\");
foreach (string file in files)
{
foreach(string text in GetLinks(File.ReadAllText(file)))
{
if (!videosLinks.Contains(text))
{
videosLinks.Add(text);
}
}
}
下載鏈接時：
private async void btnStartDownload_Click(object sender, EventArgs e)
{
if (videosLinks.Count > 0)
{
for (int i = 0; i < videosLinks.Count; i )
{
string fileName = System.IO.Path.GetFileName(videosLinks[i]);
await DownloadFile(videosLinks[i], @"D:\Videos\videos\" fileName);
}
}
}
但檔案名我想成為每個鏈接的描述。
uj5u.com熱心網友回復：
您可以使用Html Agility Pack，它是一個用 C# 撰寫的 HTML 決議器來讀/寫 DOM，并支持普通的 XPATH 或 XSLT。在下面的示例中，您可以檢索alt屬性和其他中的描述。
執行：
using HtmlAgilityPack;
using System;
public class Program
{
public static void Main()
{
HtmlDocument doc = new HtmlDocument();
var html = "<img src=\"https://thumbs.com/thumbs/test.mp4/test1.mp4-3.jpg\" alt=\"This is the description i want to get too\" >";
doc.LoadHtml(html);
HtmlNode image = doc.DocumentNode.SelectSingleNode("//img");
Console.WriteLine("Source: {0}", image.Attributes["src"].Value);
Console.WriteLine("Description: {0}", image.Attributes["alt"].Value);
Console.Read();
}
}
演示：
https ://dotnetfiddle.net/nAAZDL
輸出：
Source: https://thumbs.com/thumbs/test.mp4/test1.mp4-3.jpg
Description: This is the description i want to get too
uj5u.com熱心網友回復：
易卜拉欣的回答顯示了使用適當的 HTML 決議器是多么簡單，但我想如果您只想從單個頁面中提取單個標簽，或者不想使用外部依賴項，那么正則運算式并非不合理，尤其是如果您可以對要匹配的 HTML 做出某些假設。
請注意，下面的模式和代碼僅用于演示目的，并不意味著是一個健壯、詳盡的標簽決議器；讀者可以根據需要對它們進行擴充，以處理他們在狂野的網路中可能遇到的各種 HTML 怪癖和特性。 例如，該模式不會匹配帶有單引號或根本沒有引號的屬性值的影像標簽，并且如果標簽具有多個同名的屬性，則代碼會拋出例外。
我這樣做的方法是使用一個匹配<img />標簽及其所有屬性對的模式......
<img(?:\s (?<name>[a-z] )="(?<value>[^"]*)")*\s*/?>
...然后您可以查詢以找到您關心的屬性。您將使用該模式將影像屬性提取為Dictionary<string, string>這樣的...
static IEnumerable<Dictionary<string, string>> EnumerateImageTags(string input)
{
const string pattern =
@"
<img # Start of tag
(?: # Attribute name/value pair: noncapturing group
\s # One or more whitespace characters
(?<name>[a-z] ) # Attribute name: one or more letters
= # Literal equals sign
"" # Literal double quote
(?<value>[^""]*) # Attribute value: zero or more non-double quote characters
"" # Literal double quote
)* # Zero or more attributes are allowed
\s* # Zero or more whitespace characters
/?> # End of tag with optional forward slash
";
foreach (Match match in Regex.Matches(input, pattern, RegexOptions.IgnorePatternWhitespace))
{
string[] attributeValues = match.Groups["value"].Captures
.Cast<Capture>()
.Select(capture => capture.Value)
.ToArray();
// Create a case-insensitive dictionary mapping from each capture of the "name" group to the same-indexed capture of the "value" group
Dictionary<string, string> attributes = match.Groups["name"].Captures
.Cast<Capture>()
.Select((capture, index) => new KeyValuePair<string, string>(capture.Value, attributeValues[index]))
.ToDictionary(pair => pair.Key, pair => pair.Value, StringComparer.OrdinalIgnoreCase);
yield return attributes;
}
}
鑒于SO74133924.html...
<html>
<body>
<p>This image comes from https://thumbs.com/thumbs/test.mp4/test1.mp4-3.jpg:
<img src="https://thumbs.com/thumbs/test.mp4/test1.mp4-3.jpg" alt="This is the description i want to get too">
<p>This image has additional attributes on multiple lines in a self-closing tag:
<img
first="abc"
src="https://thumbs.com/thumbs/test.mp4/test1.mp4-3.jpg"
empty=""
alt="This image has additional attributes on multiple lines in a self-closing tag"
last="xyz"
/>
<p>This image has empty alternate text:
<img src="https://example.com/?message=This image has empty alternate text" alt="">
<p>This image has no alternate text:
<img src="https://example.com/?message=This image has no alternate text">
</body>
</html>
...您會像這樣使用每個標簽的屬性字典...
static void Main()
{
string input = File.ReadAllText("SO74133924.html");
foreach (Dictionary<string, string> imageAttributes in EnumerateImageTags(input))
{
foreach (string attributeName in new string[] { "src", "alt" })
{
string displayValue = imageAttributes.TryGetValue(attributeName, out string attributeValue)
? $"\"{attributeValue}\"" : "(null)";
Console.WriteLine($"{attributeName}: {displayValue}");
}
Console.WriteLine();
}
}
...輸出這個...
src：“https://thumbs.com/thumbs/test.mp4/test1.mp4-3.jpg” alt：“這也是我想要得到的描述” src：“https://thumbs.com/thumbs/test.mp4/test1.mp4-3.jpg” alt：“此影像在自閉合標簽中的多行上具有附加屬性” src: "https://example.com/?message=這張圖片有空的替代文字" 替代：“” src: "https://example.com/?message=這張圖片沒有替代文字" 替代：（空）
uj5u.com熱心網友回復：
如果您使用正則運算式的代碼，它將花費更多的 CPU 周期并且執行速度很慢。使用像 AngleSharp 這樣的庫。
我試圖用 AngleSharp 撰寫你的代碼。我就是這樣做的。
string test = "<img src=\"https://thumbs.com/thumbs/test.mp4/test1.mp4-3.jpg\" alt=\"This is the description i want to get too\" >\r\n";
var configuration = Configuration.Default.WithDefaultLoader();
var context = BrowsingContext.New(configuration);
using var doc = await context.OpenAsync(req => req.Content(test));
string href = doc.QuerySelector("img").Attributes["alt"].Value;
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