C # delegate implementation of the Child Window to call the parent window control

Sometimes the sub-form operation needs to call the control operation in the parent form in real time, for example, display the output in the sub-form in the text box of the parent form:

 

Main form:

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2. Mainform. CS:
6. PublicPartialClassMainform: Form
8. {
10. PublicMainform ()
12. {
14. Initializecomponent ();
16. }
20. Private VoidButton#click (ObjectSender, eventargs E)
22. {
24. Subform =NewSubform ();
28. // 3. Add changetextval to the delegate event
30. // Equivalent:
32. // Subform. changetextval + = changetextval;
34. Subform. changetextval + =NewDelegatechangetextval (changetextval );
36. Subform. showdialog ();
38. }
42. Public VoidChangetextval (StringTextval)
44. {
46. This. Textbox1.text = textval;
48. }
50. }

Subform:

 

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2. Subform. CS:
6. // 1. Define the delegate type
8. Public Delegate VoidDelegatechangetextval (StringTextval );
12. PublicPartialClassSubform: Form
14. {
16. // 2. Define a delegate event
18. Public EventDelegatechangetextval changetextval;
22. PublicSubform ()
24. {
26. Initializecomponent ();
28. }
32. Private VoidButton#click (ObjectSender, eventargs E)
34. {
36. Changemainformtext (This. Textbox1.text );
38. }
42. Private VoidChangemainformtext (StringTextval)
44. {
46. // 4. Call the delegate event Function
48. Changetextval (textval );
50. }
52. }