I’m seeing some odd behaviour with Blazor with event hooks and the firstRender argument of OnAfterRender.

My parent component creates a dynamic set of child components:

Parent:

@if (_childObjects != null)
{
    @foreach (var childObject in _childObjects )
    {
        <ChildComponent ChildObject=@childObject />
     }
 }     

Child:

[Parameter]
public ChildObject ChildObject { get; set;  }

What happens is on clicking certain buttons that parent re-renders with a new set of child objects. I expect it to create new instances of ChildComponent for that, which it partially does.

But somehow when it hits this code:

protected override void OnAfterRender(bool firstRender)

… at this point, the value of firstRender is false and everything seems to be already initialised as per the previous render of the parent.

>Solution :

I expect it to create new instances of ChildComponent

Why? Blazor sees a (Child) Component with a different parameter.

You can help the differ by adding @key, I think that will do what you want:

@foreach (var childObject in _childObjects )
{
    <ChildComponent @key="childObject" ChildObject="childObject" />
 }