C# 如何在我的电子邮件验证中读取正则表达式

我找到了一个使用regex验证电子邮件的解决方案。 但我真的不明白如何正确阅读它，因为这是我第一次使用regex。 谁能给我解释一下怎样用文字读它吗？因为用if语句创建这个将是一件痛苦的事

我的代码：

if (string.IsNullOrWhiteSpace(textBox4.Text))
{
    label8.Text = "E-pasts netika ievadīts!";
}
else
{
    Regex emailExpression = new Regex(@"^[a-zA-Z][\w\.-]{2,28}[a-zA-Z0-9]@[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]\.[a-zA-Z][a-zA-Z\.]*[a-zA-Z]$");
    if (emailExpression.IsMatch(textBox4.Text))
    {
        label8.Text = "";
    }
    else
    {
        label8.Text = "E-pasts ievadīts nepareizi!";
    }
}

---

对于regex，请点击以下链接：

这里粘贴您的正则表达式

[a-zA-Z][\w\.-]{2,28}[a-zA-Z0-9]@[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]\.[a-zA-Z][a-zA-Z\.]*[a-zA-Z].

将鼠标悬停在每个文本上，您将了解它们的含义

举几个例子：

a-z

将匹配a到z范围内的字符

A-Z

将匹配A-Z范围内的字符

\w

匹配任何单词字符

---

{2,28}

前面标记的2和28之间的匹配

对于正则表达式，请遵循以下链接：

这里粘贴您的正则表达式

[a-zA-Z][\w\.-]{2,28}[a-zA-Z0-9]@[a-zA-Z0-9][\w\.-]*[a-zA-Z0-9]\.[a-zA-Z][a-zA-Z\.]*[a-zA-Z].

将鼠标悬停在每个文本上，您将了解它们的含义

举几个例子：

a-z

将匹配a到z范围内的字符

A-Z

将匹配A-Z范围内的字符

\w

匹配任何单词字符

---

{2,28}

前面标记的2和28之间的匹配

以下是细分。请注意，所有

[]

都是单个项目的集合。以下可以是

*

（零或多个）或

+

一个或多个或

{，}

（最小和最大）事件

如果一个人评论模式以显示一个固有的模式，那么一旦在关键点上做了标记，实际上更容易理解；我将这样做：

var pattern = @"
^                  # Beginning of line, data must start here instead of matching any location *away from the start*.
      [a-zA-Z]         # A set of characters from a-z and A-Z but just one
      [\w\.-]{2,28}    # A set of any word character \w=a-zA-Z0-9 with a literal period and dash; but minimum of 2 to a max of 28 characters. 
      [a-zA-Z0-9]      # Could be replaced with a single \w; this ensure that there is a character and not a non character before the @
  @                # Literal `@`
      [a-zA-Z0-9]      # same as \w; ensures a character
      [\w\.-]*         # '*' = Zero or more of the set with a literal period in the set.
      [a-zA-Z0-9]      # same as \w; ensures a character
 \.                # Literal Period must be matched.
      [a-zA-Z]         # A set of characters from a-z and A-Z but just one
      [a-zA-Z\.]*      # zero or more characters with a literal period `.`.
      [a-zA-Z]         # same as \w; ensures a character
$                  # End; contrains the whole match with the `^` so no loose characters are left out of the match
";

// IgnorePatternWhitespace allows us to comment the pattern; does not affect processing in any way.
Regex.IsMatch("abcd@def.com", pattern, RegexOptions.IgnorePatternWhitespace); // True/Valid
Regex.IsMatch("1abcd@def.com", pattern, RegexOptions.IgnorePatternWhitespace);// False/Invalid
Regex.IsMatch("abc@def.com", pattern, RegexOptions.IgnorePatternWhitespace);  // False/Invalid

---

---

注意，测试#3中发现的模式中存在逻辑缺陷。对于

abc@def.com

将失败，因为模式在

@

之前的第一个字符和最后一个字符前缀之间至少查找2个字符。我会把它改成一个

*

，意思是零或更多。

这里是分类。请注意，所有

[]

都是单个项目的集合。以下可以是

*

（零或多个）或

+

一个或多个或

{，}

（最小和最大）事件

如果一个人评论模式以显示一个固有的模式，那么一旦在关键点上做了标记，实际上更容易理解；我将这样做：

var pattern = @"
^                  # Beginning of line, data must start here instead of matching any location *away from the start*.
      [a-zA-Z]         # A set of characters from a-z and A-Z but just one
      [\w\.-]{2,28}    # A set of any word character \w=a-zA-Z0-9 with a literal period and dash; but minimum of 2 to a max of 28 characters. 
      [a-zA-Z0-9]      # Could be replaced with a single \w; this ensure that there is a character and not a non character before the @
  @                # Literal `@`
      [a-zA-Z0-9]      # same as \w; ensures a character
      [\w\.-]*         # '*' = Zero or more of the set with a literal period in the set.
      [a-zA-Z0-9]      # same as \w; ensures a character
 \.                # Literal Period must be matched.
      [a-zA-Z]         # A set of characters from a-z and A-Z but just one
      [a-zA-Z\.]*      # zero or more characters with a literal period `.`.
      [a-zA-Z]         # same as \w; ensures a character
$                  # End; contrains the whole match with the `^` so no loose characters are left out of the match
";

// IgnorePatternWhitespace allows us to comment the pattern; does not affect processing in any way.
Regex.IsMatch("abcd@def.com", pattern, RegexOptions.IgnorePatternWhitespace); // True/Valid
Regex.IsMatch("1abcd@def.com", pattern, RegexOptions.IgnorePatternWhitespace);// False/Invalid
Regex.IsMatch("abc@def.com", pattern, RegexOptions.IgnorePatternWhitespace);  // False/Invalid

---

---

注意，测试#3中发现的模式中存在逻辑缺陷。对于

abc@def.com

将失败，因为模式在

@

之前的第一个字符和最后一个字符前缀之间至少查找2个字符。我会改为

*

，意思是零或更多。

我可以推荐LeaVerou关于正则表达式的演讲。看，我可以推荐Lea Verou关于regex的演讲。看见