C#基础知识之字符串和正则表达式的案例分享

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string messagel = ''Hello"; // returns "Hello" messagel += ”,There";   // returns "Hello, There"string message2 = messagel + "!";  // returns "Hello, There! "

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string message = ''Hello”；char char4 = message[4]; // returns "0"

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string greetingText = "Hello from all the people at Wrox Press.greetingText += **We do hope you enjoy this book as much as we enjoyed writing it.";

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var sb = new StringBuilder("Hello");

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string si = "World"; string s2 = $"Hello, {s1}“;

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string si = "World";string s2 = String.Format("Hello, {0}", si);

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string s2 = $”Hello, {<!--{C}%3C!%2D%2D%20%2D%2D%3E-->si. ToUpper() } '*;

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string s2 = String.Format(nHello, {<!--{C}%3C!%2D%2D%20%2D%2D%3E-->0}”，si.ToUpper ());

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int x = 3, y = 4;string s3 = $"MThe result of {x} + {y}  is {x + y}'";

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string s3 = String.Format("The result of {0} and {1} is {2 } ", x, y, x + y);

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string s = "Hello";Console.WriteLine($"{{s}}  displays the value of s:   {s}");

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Console.WriteLine (String.Format (*'{<!--{C}%3C!%2D%2D%20%2D%2D%3E-->s} displays the value of s: {<!--{C}%3C!%2D%2D%20%2D%2D%3E-->0}", s));

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string formatstring = $" {s},   {{0 } } "; string s2 = "World";WriteLine(formatstring, s2);

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string formatstring = String. Format ("{0}, {<!--{C}%3C!%2D%2D%20%2D%2D%3E-->{0} } ", s);

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string formatstring = "Hello, {0}";

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WriteLine("Hello, World");

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var day = new DateTime(2025, 2, 14); WriteLine ($"{day:D}")；WriteLine ($"{day:d}”);

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Friday, February 14, 2025 2/14/2025

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Console.WriteLine($"{day:dd-MMM-yyyy}");

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int i = 2477;Console.WriteLine($"{i：n} {i:e} {i:x} {i:c}H);

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const string text =            "Professional C# 6 and .NET Core 1.0 provides complete coverage " +            "of the latest updates, features, and capabilities, giving you " +            "everything you need for C#. Get expert instruction on the latest " +            "changes to Visual Studio 2015, Windows Runtime, ADO.NET, ASP.NET, " +            "Windows Store Apps, Windows Workflow Foundation, and more, with " +            "clear explanations, no-nonsense pacing, and valuable expert insight. " +            "This incredibly useful guide serves as both tutorial and desk " +            "reference, providing a professional-level review of C# architecture " +            "and its application in a number of areas. You'll gain a solid " +            "background in managed code and .NET constructs within the context of " +            "the 2015 release, so you can get acclimated quickly and get back to work.";Console.WriteLine("Find1\n");const string pattern = "ion"; MatchCollection matches = Regex.Matches(text, pattern,                                        RegexOptions.IgnoreCase |                                        RegexOptions.ExplicitCapture);WriteMatches(text, matches);Console.WriteLine();

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public static void NamedGroups(){     Console.WriteLine("NamedGroups\n");     string line = "Hey, I've just found this amazing URI at http:// what was it --oh yes https://www.wrox.com or http://www.wrox.com:80";      string pattern = @"\b(?<protocol>https?)(?:://)(?<address>[.\w]+)([\s:](?<port>[\d]{2,4})?)\b";     Regex r = new Regex(pattern, RegexOptions.ExplicitCapture);      MatchCollection mc = r.Matches(line);     foreach (Match m in mc)     {         Console.WriteLine($"match: {m} at {m.Index}");          foreach (var groupName in r.GetGroupNames())         {             Console.WriteLine($"match for {groupName}: {m.Groups[groupName].Value}");         }         Console.WriteLine();     }     Console.WriteLine();}