Frequently Used String Extension Methods in C#

Introduction

You may have learned about extension methods in my previous article Extension Method In C# that explained their step-by-step implementation. Therefore, we will now go straight to code.

1. Create a static class StringExtension that contains an extension method. This extension method converts a title in a SEO friendly URL.
   
   1. using System.Collections.Generic;
   2. using System.Text;
   3. using System.Text.RegularExpressions;
   5. namespace ExtensionMethod
   6. {
   7. public static class StringExtension
   8. {
   9. public static string SeoFriendlyURL(this string title, int maxLength)
   10. {
   11. Dictionary<string, string> dictWords = new Dictionary<string, string>{
   12. {"C#","c-sharp"},
   13. {"F#","f-sharp"}
   14. };
   16. foreach (KeyValuePair<string, string> word in dictWords)
   17. {
   18. title = title.Replace(word.Key, word.Value);
   19. }
   21. var match = Regex.Match(title.ToLower(), "[\\w]+");
   22. StringBuilder seoUrl = new StringBuilder("");
   23. bool maxLengthHit = false;
   24. while (match.Success && !maxLengthHit)
   25. {
   26. if (seoUrl.Length + match.Value.Length <= maxLength)
   27. {
   28. seoUrl.Append(match.Value + "-");
   29. }
   30. else
   31. {
   32. maxLengthHit = true;
   33. if (seoUrl.Length == 0)
   34. {
   35. seoUrl.Append(match.Value.Substring(0, maxLength));
   36. }
   37. }
   38. match = match.NextMatch();
   39. }
   40. if (seoUrl[seoUrl.Length - 1] == '-')
   41. {
   42. seoUrl.Remove(seoUrl.Length - 1, 1);
   43. }
   44. return seoUrl.ToString();
   45. }
   46. }
   47. }
2. The following code snippet shows how to call it.
   
   1. using System;
   3. namespace ExtensionMethod
   4. {
   5. class Program
   6. {
   7. static void Main(string[] args)
   8. {
   9. Console.WriteLine("Enter the Title");
   10. string title = Console.ReadLine();
   11. string seoUrl = title.SeoFriendlyURL(100);
   12. Console.WriteLine("Seo url is: {0}", seoUrl);
   13. Console.ReadKey();
   14. }
   15. }
   16. }
   
   Figure 1.1 : Output for SEO friendly URL

String Exists in String Array

Here we check a string that either exists or not in a defined array.

1. Create a static class StringExtension that contains an extension method. This extension method returns a true value if the string exists in a defined array else returns false.
   
   1. using System;
   2. using System.Linq;
   4. namespace ExtensionMethod
   5. {
   6. public static class StringExtension
   7. {
   8. public static bool IsExist(this string input, params string[] values)
   9. {
   10. return String.IsNullOrEmpty(input) ? false : values.Any(S => input.Contains(S));
   11. }
   12. }
   13. }
2. The following code snippet shows how to call it.
   
   1. using System;
   3. namespace ExtensionMethod
   4. {
   5. class Program
   6. {
   7. static void Main(string[] args)
   8. {
   9. string[] language = new string[] { "C#", "F#", "Java" };
   10. Console.WriteLine("Enter a lagunage name");
   11. string name = Console.ReadLine();
   12. bool isExist = name.IsExist(language);
   13. Console.WriteLine("{0} is exist: {1}", name, isExist);
   14. Console.WriteLine("Enter another lagunage name");
   15. name = Console.ReadLine();
   16. isExist = name.IsExist(language);
   17. Console.WriteLine("{0} is exist: {1}", name, isExist);
   18. Console.ReadKey();
   19. }
   20. }
   21. }
   
   Figure 1.2: Output Extension method

1. Create a static class StringExtension that contains an extension method. This extension method returns either a dotted string or the full string depending on the conditions.
   
   1. using System;
   2. using System.Linq;
   4. namespace ExtensionMethod
   5. {
   6. public static class StringExtension
   7. {
   8. public static string DottedString(this string input, int length, bool Incomplete = true)
   9. {
   10. if (String.IsNullOrEmpty(input))
   11. {
   12. return String.Empty;
   13. }
   14. return input.Length > length ? String.Concat(input.Substring(0, length), Incomplete ? "..." : "") : input;
   15. }
   16. }
   17. }
2. The following code snippet shows how to call it.
   
   1. using System;
   3. namespace ExtensionMethod
   4. {
   5. class Program
   6. {
   7. static void Main(string[] args)
   8. {
   9. Console.WriteLine("Enter a string value");
   10. string value = Console.ReadLine();
   11. string dottedString = value.DottedString(5);
   12. Console.WriteLine("{0} is converted: {1}", value, dottedString);
   13. Console.WriteLine("Enter another string value");
   14. value = Console.ReadLine();
   15. dottedString = value.DottedString(5, false);//trim without dot
   16. Console.WriteLine("{0} is converted: {1}", value, dottedString);
   17. Console.ReadKey();
   18. }
   19. }
   20. }
   
   Figure 1.3: Output for dotted string