In this article, we will continue from the previous article and see a few examples around the UI side. Let us suppose the following snippet, wherein I have simply created one windows form and attached a textbox to it.
  1. using System;
  2. using System.Reactive.Linq;
  3. using System.Windows.Forms;
  5. namespace ReactiveExtensions
  6. {
  7. internal class Program
  8. {
  9. private static void Main(string[] args)
  10. {
  11. // ObservableGetValue();
  12. var textbox = new TextBox();
  13. var form = new Form
  14. {
  15. Controls = {textbox}
  16. };
  18. Application.Run(form);
  19. }
  22. private static void ObservableGetValue()
  23. {
  24. IObservable<string> obj = Observable.Generate(
  25. 0, //Sets the initial value like for loop
  26. _ => true, //Don't stop till i say so, infinite loop
  27. i => i + 1, //Increment the counter by 1 everytime
  28. i => new string('#', i), //Append #
  29. i => TimeSelector(i)); //delegated this to private method which just calculates time
  31. //Subscribe here
  32. using (obj.Subscribe(Console.WriteLine))
  33. {
  34. Console.WriteLine("Press any key to exit!!!");
  35. Console.ReadLine();
  36. }
  37. }
  39. //Returns TimeSelector
  40. private static TimeSpan TimeSelector(int i)
  41. {
  42. return TimeSpan.FromSeconds(i);
  43. }
  44. }
  45. }
Now, with the above change in place, it will simply give me one window form with one text-box in it.
text box
Now, I would like to listen to text changed event. So, what I would do? I will simply go ahead and attach the text changed handler as in the following code snippet.
textchanged
Therefore, it has created the following sample event code.
  1. using System;
  2. using System.Reactive.Linq;
  3. using System.Windows.Forms;
  5. namespace ReactiveExtensions
  6. {
  7. internal class Program
  8. {
  9. private static void Main(string[] args)
  10. {
  11. // ObservableGetValue();
  12. var textbox = new TextBox();
  13. var form = new Form
  14. {
  15. Controls = {textbox}
  16. };
  18. //Trying to fetch the value from textbox
  19. textbox.TextChanged += textbox_TextChanged;
  21. Application.Run(form);
  22. }
  24. static void textbox_TextChanged(object sender, EventArgs e)
  25. {
  26. throw new NotImplementedException();
  27. }
  30. private static void ObservableGetValue()
  31. {
  32. IObservable<string> obj = Observable.Generate(
  33. 0, //Sets the initial value like for loop
  34. _ => true, //Don't stop till i say so, infinite loop
  35. i => i + 1, //Increment the counter by 1 everytime
  36. i => new string('#', i), //Append #
  37. i => TimeSelector(i)); //delegated this to private method which just calculates time
  39. //Subscribe here
  40. using (obj.Subscribe(Console.WriteLine))
  41. {
  42. Console.WriteLine("Press any key to exit!!!");
  43. Console.ReadLine();
  44. }
  45. }
  47. //Returns TimeSelector
  48. private static TimeSpan TimeSelector(int i)
  49. {
  50. return TimeSpan.FromSeconds(i);
  51. }
  52. }
  53. }
But, if you look at the following screenshot, textchanged is not available.
code
Hence, this won't be helpful to me. Rather than that, I would prefer to have a reactive extension and subscribe the same as shown below.
  1. private static void Main(string[] args)
  2. {
  3. // ObservableGetValue();
  4. var textbox = new TextBox();
  5. var form = new Form
  6. {
  7. Controls = {textbox}
  8. };
  10. //Using Rx, to get the textchanged
  12. var textChanged = Observable.FromEventPattern<EventArgs>(textbox, "TextChanged");
  14. //then, I will subscribe the same
  16. Application.Run(form);
  17. }
Now, if you see the following screenshot, it gave me EventArgs.
EventArgs
really
Here, in order to get changed text, I need to make use of LINQ on the top of Rx. Hence, below is the finished code for the same. I have done a little bit of refactoring as well, just to keep the code more readable and clean.
  1. using System;
  2. using System.Reactive.Linq;
  3. using System.Windows.Forms;
  5. namespace ReactiveExtensions
  6. {
  7. internal class Program
  8. {
  9. private static void Main(string[] args)
  10. {
  11. // ObservableGetValue();
  12. GetTextBoxValue();
  13. }
  15. private static void GetTextBoxValue()
  16. {
  17. var textbox = new TextBox();
  18. var form = new Form
  19. {
  20. Controls = {textbox}
  21. };
  23. //Using Rx, to get the textchanged
  25. var textChanged = Observable.FromEventPattern<EventArgs>(textbox, "TextChanged");
  27. //then, I will subscribe the same using LINQ Projection
  29. var query = from e in textChanged
  30. select ((TextBox) e.Sender).Text;
  32. //Hence, if the application quits, i want to unsubscribe
  33. using (query.Subscribe(Console.WriteLine))
  34. {
  35. Application.Run(form);
  36. }
  37. }
  40. private static void ObservableGetValue()
  41. {
  42. IObservable<string> obj = Observable.Generate(
  43. 0, //Sets the initial value like for loop
  44. _ => true, //Don't stop till i say so, infinite loop
  45. i => i + 1, //Increment the counter by 1 everytime
  46. i => new string('#', i), //Append #
  47. i => TimeSelector(i)); //delegated this to private method which just calculates time
  49. //Subscribe here
  50. using (obj.Subscribe(Console.WriteLine))
  51. {
  52. Console.WriteLine("Press any key to exit!!!");
  53. Console.ReadLine();
  54. }
  55. }
  57. //Returns TimeSelector
  58. private static TimeSpan TimeSelector(int i)
  59. {
  60. return TimeSpan.FromSeconds(i);
  61. }
  62. }
  63. }
Hence, with the above change in place, when I run the app, it will give us the following output.
run the app
You can also download the source code from here.
With this, I would like to wrap this session here. Thanks for joining me.