Blazor server side onmousemove causes component rerender

[rborosak]

I have added onmousemove to a div. It is bound to a method that does some calculation if the mouse is pressed but I have noticed that the component rerenders even when the metod is empty.

<div @onmousemove="@OnMouseMove">I'm a div content</div>

@code{
    public void OnMouseMove(MouseEventArgs e){
        //empty method but it causes a rerender
    }

    protected override void OnAfterRender(bool firstRender){
        Debug.WriteLine("Rendered!")
    }
}

I have tried to change onmousemove="@OnMouseMove" to onmousemove="@((e)=>OnMouseMove(e))" but I still get the same result.
Every time a mouse enters a div, "Rendered" is written to console meaning that the component has rerendered.

Why is this happening? Is there any workaround?

I'm using Blazor server side with ASP.NET Core version 3.0 and VisualStudio 2019.

[javiercn]

@rborosak thanks for contacting us.

Blazor triggers an automatic re-render of a component as part of dispatching an event to it. If you want to alter this behavior you can override the ShouldRender method on ComponentBase to selectively choose when to re-render the component.