I will demonstrate how to reverse a string in a simple way and how to find a specfic word in the given string using C#. Here is the code sample that shows you how to reverse a string in C# and find the desired word in a given string.
Reverse a string in simple steps using C#.
  1. public string ReverseString(string input)
  2. {
  3. if (string.IsNullOrEmpty(input))
  4. {
  5. throw new ArgumentNullException();
  6. }
  8. var output = input.Reverse();
  9. return new string(output.ToArray());
  10. }
Find a word in given string. We assume the separator of word is space (' ');
  1. /// Example 1: GetWordFromText("one two three", 2) should return "two"
  2. /// Example 2: GetWordFromText("one;two three", 2) should return "three"
  3. /// Example 3: GetWordFromText("one", 1) should return "one"
  4. /// When input parameter wordNumberToFind is less than 1, method should throw
  5. /// ArgumentOutOfRangeException. When input text does not have enough words
  6. /// (GetWordFromText("one", 2)), method should throw ArgumentException.
  7. /// When input is null method should throw `ArgumentNullException`.
  8. /// Method should ignore all spaces in the beginning and in the end of input text.
  9. /// </returns>
  10. public string GetWordFromText(string input, int wordNumberToFind)
  11. {
  13. // TODO: Implement logic HERE
  14. if (wordNumberToFind < 1)
  15. {
  16. throw new ArgumentOutOfRangeException();
  17. }
  19. if (string.IsNullOrWhiteSpace(input))
  20. {
  21. throw new ArgumentNullException();
  22. }
  24. var words = input.Split(' ');
  26. if (wordNumberToFind > words.Length)
  27. {
  28. throw new ArgumentException();
  29. }
  31. while (string.IsNullOrWhiteSpace(words[wordNumberToFind - 1]))
  32. {
  33. wordNumberToFind++;
  34. }
  36. return words[wordNumberToFind - 1];
  37. }
Let's have some unit tests to verify the above code.
  1. namespace TaskLib.Tests
  2. {
  3. using System;
  5. using FluentAssertions;
  6. using NUnit.Framework;
  8. [TestFixture]
  9. public class StringTests
  10. {
  11. [Test]
  12. public void When_WordToFindIsNotInTheInput_Then_ArgumentExceptionIsThrown()
  13. {
  14. // Arrange
  15. var tested = new StringHelpers();
  17. // Act
  18. Assert.Throws<ArgumentException>(() => { var word = tested.GetWordFromText("two words", 3); });
  19. }
  21. [Test]
  22. public void When_InputTextContainsFewWords_Then_ProperOneIsReturned()
  23. {
  24. // Arrange
  25. var tested = new StringHelpers();
  27. // Act
  28. var word = tested.GetWordFromText("one;two three", 2);
  30. // Assert
  31. word.Should().Be("three");
  32. }
  34. [Test]
  35. public void When_InputTextIsSymmetrical_Then_ItIsReturned()
  36. {
  37. // Arrange
  38. var tested = new StringHelpers();
  40. // Act
  41. var reversed = tested.Reverse("evil live");
  43. // Assert
  44. reversed.Should().Be("evil live");
  45. }
  47. [Test]
  48. public void When_InputTextIsPassed_Then_ItIsReversed()
  49. {
  50. // Arrange
  51. var tested = new StringHelpers();
  53. // Act
  54. var reversed = tested.Reverse("abcd efgh");
  56. // Assert
  57. reversed.Should().Be("hgfe dcba");
  58. }
  59. }
  60. }
Thanks. I hope you liked this simple approach of reversing a string and finding a word in the string.