What are Invoke & InvokeAsync methods?

Question

What is Invoke methods?

Below here is my viewcomponent() method.

public IViewComponentResult Invoke()
{
 ViewBag.SelectedCategory = RouteData?.Values["category"];
return 
View(repository.Products.Select(x=>x.Category).Distinct().OrderBy(x=>x));
}

Is this is the anonymous function?

what is the name of this function ?

I tried to change "Invoke" with "func" but there is no syntax error but run-time error Occurred.

Is it Possible to have multiple methods with "Invoke" name and receiving different parameters In a single view component class.

I Know that view component use to render partial views for this we use helper which is this

 @await Component.InvokeAsync("Here is the name of your view component")

"component.InvokeAsynk" Goes to your component class and finds The Invoke method and then follows this method

Answer 1

The Invoke and InvokeAsync methods on a ViewComponent are the methods that define the logic of the view component. These are not anonymous functions. They are regular c# methods that simply have the names Invoke and InvokeAsync.

You don't need to define both of them in your view component. On the contrary you can only define one method.

Let us say you named it Invoke and then you rename it to func then you have changed the name of the method:

• you won't get a compiler error, but
• a runtime error will occur.

This is because the Asp.Net Core framework code that calls your view component expects it to have either a Invoke or InvokeAsync method and your ViewComponent now has neither.

You can name your view component anything you like but the name of the method which gets called to invoke it must be called Invoke or InvokeAsync.

A ViewComponent can only have one Invoke or InvokeAsync method. A ViewComponent can't have both and it can't multiples of either one (with different parameters). Attempting to do so will produce the following runtime error:

View component 'ViewComponents.NameOfComponent' must have exactly one public method named 'InvokeAsync' or 'Invoke'.