这个问题开始流行起来，出现了很多有趣的建议。
是的，手写很难。所以更简单的解决方案是使用模板。尽管生成的正则表达式可能不是最佳的，但它会更容易维护和/或更改，并且用户将对结果有更好的控制。我可能遗漏了什么，所以任何建设性的批评都会有所帮助。
此链接可能很有趣：match at least 2 digits 2 letters in any order in a string、Regular Expression Language、Capturing groups
我正在使用这个模板(?=(?:.*?({type})){({count})})，基于我在 SO 中看到的所有正则表达式。下一步是替换所需的模式（number、special character ...）并添加长度配置。
我为编写正则表达式 PasswordRegexGenerator.cs 做了一个小课
一个例子：
string result = new PasswordRegexGenerator ( )
.UpperCase ( 3, -1 ) // ... {3,}
.Number ( 2, 4 ) // ... {2,4}
.SpecialCharacter ( 2 ) // ... {2}
.Total ( 8,-1 )
.Compose ( );
/// <summary>
/// Generator for regular expression, validating password requirements.
/// </summary>
public class PasswordRegexGenerator
{
private string _elementTemplate = "(?=(?:.*?({type})){({count})})";
private Dictionary<string, string> _elements = new Dictionary<string, string> {
{ "uppercase", "[A-Z]" },
{ "lowercase", "[a-z]" },
{ "number", @"\d" },
{ "special", @"\W" },
{ "alphanumeric", @"\w" }
};
private StringBuilder _sb = new StringBuilder ( );
private string Construct ( string what, int min, int max )
{
StringBuilder sb = new StringBuilder ( _elementTemplate );
string count = min.ToString ( );
if ( max == -1 )
{
count += ",";
}
else if ( max > 0 )
{
count += "," + max.ToString();
}
return sb
.Replace ( "({type})", what )
.Replace ( "({count})", count )
.ToString ( );
}
/// <summary>
/// Change the template for the generation of the regex parts
/// </summary>
/// <param name="newTemplate">the new template</param>
/// <returns></returns>
public PasswordRegexGenerator ChangeRegexTemplate ( string newTemplate )
{
_elementTemplate = newTemplate;
return this;
}
/// <summary>
/// Change or update the regex for a certain type ( number, uppercase ... )
/// </summary>
/// <param name="name">type of the regex</param>
/// <param name="regex">new value for the regex</param>
/// <returns></returns>
public PasswordRegexGenerator ChangeRegexElements ( string name, string regex )
{
if ( _elements.ContainsKey ( name ) )
{
_elements[ name ] = regex;
}
else
{
_elements.Add ( name, regex );
}
return this;
}
#region construction methods
/// <summary>
/// Adding number requirement
/// </summary>
/// <param name="min"></param>
/// <param name="max"></param>
/// <returns></returns>
public PasswordRegexGenerator Number ( int min = 1, int max = 0 )
{
_sb.Append ( Construct ( _elements[ "number" ], min, max ) );
return this;
}
public PasswordRegexGenerator UpperCase ( int min = 1, int max = 0 )
{
_sb.Append ( Construct ( _elements[ "uppercase" ], min, max ) );
return this;
}
public PasswordRegexGenerator LowerCase ( int min = 1, int max = 0 )
{
_sb.Append ( Construct ( _elements[ "lowercase" ], min, max ) );
return this;
}
public PasswordRegexGenerator SpecialCharacter ( int min = 1, int max = 0 )
{
_sb.Append ( Construct ( _elements[ "special" ], min, max ) );
return this;
}
public PasswordRegexGenerator Total ( int min, int max = 0 )
{
string count = min.ToString ( ) + ( ( max == 0 ) ? "" : "," + max.ToString ( ) );
_sb.Append ( ".{" + count + "}" );
return this;
}
#endregion
public string Compose ()
{
return "(" + _sb.ToString ( ) + ")";
}
}