.NET Regular Expressions

private static readonly Regex REGEX_LINE_BREAKS = new Regex(@"\n\s*", RegexOptions.Compiled);
private static readonly Regex REGEX_LINE_SPACE = new Regex(@"\n\s*\r", RegexOptions.Compiled);
private static readonly Regex REGEX_SPACE = new Regex(@"( )+", RegexOptions.Compiled);

var targetHtml = REGEX_SPACE.Replace(REGEX_LINE_SPACE.Replace(REGEX_LINE_BREAKS.Replace(baseInfoHtml, ""), ""), " ");

Ref:正则表达式30分钟入门教程

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Ref:Matching Balanced Constructs with .NET Regular Expressions

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Ref:http://regexlib.com/Default.aspx