Task, Thread, Events, Action, Func, Pred, Delgates

Question

Hello,
https://dotnetpattern.com/csharp-action-delegate
https://dotnetpattern.com/csharp-predicate-delegate

I found this.
Maybe you still know good sites or have explanations here. Would be nice.

The main question is
When do I take what? That there is, is already clear.
What are the criteria for the choice?

Answer 1

I will pick Action and Func,

Example for Action, we are performing an task in a class which the caller a form, subscribes to the event which adds a string to a ListBox, to prevent cross threading we must use .Invoke.

The action in the extension method is lb => { listBox2.Items.Add(name);}, in the extension method .Invoke adds the item.

// in the form  
public async Task IterateContactNames()  
{  
	await foreach (var name in DataOperations.GetAllNamesPaged(true))  
	{  
		listBox2.InvokeIfRequired(lb => { listBox2.Items.Add(name);});  
	}  
}  
  
public static class Extensions  
{  
	public static void InvokeIfRequired<T>(this T control, Action<T> action) where T : ISynchronizeInvoke  
	{  
		if (control.InvokeRequired)  
		{  
			control.Invoke(new Action(() => action(control)), null);  
		}  
		else  
		{  
			action(control);  
		}  
	}  
}  

For Func, a simple example, here we pass in an instance of StudentGrade and return a DTO, StudentEntity, pass in one type below and get another type back,

public partial class StudentGrade  
{  
  
	public static Expression<Func<StudentGrade, StudentEntity>> Projection  
	{  
		get  
		{  
			return (student) => new StudentEntity()  
			{  
				PersonID = student.StudentID,  
				CourseID = student.CourseID,  
				FirstName = student.Student.FirstName,  
				LastName = student.Student.LastName,  
				Grade = student.Grade  
			};  
		}  
	}  
}  

All of these Task, Thread, Events, Action, Func, Pred, Delgates are best understood by reading the docs, finding examples and inspecting them. If I were to answer each one in depth this is not the place to do it and can be ad nauseam.