Blazor WASM perf ShouldRender updates (#18957)

Author: guardrex

aspnetcore/blazor/webassembly-performance-best-practices.md

@@ -5,7 +5,7 @@ description: Tips for increasing performance in ASP.NET Core Blazor WebAssembly
 monikerRange: '>= aspnetcore-2.1'
 ms.author: riande
 ms.custom: mvc
-ms.date: 06/08/2020
+ms.date: 06/25/2020
 no-loc: [Blazor, "Identity", "Let's Encrypt", Razor, SignalR]
 uid: blazor/webassembly-performance-best-practices
 ---
@@ -27,7 +27,7 @@ If authoring a UI-only component that never changes after the initial render, co
 }
 ```
 
-Most apps don't require fine-grained control, but <xref:Microsoft.AspNetCore.Components.ComponentBase.ShouldRender%2A> can also be used to selectively render a component responding to a UI event.
+Most apps don't require fine-grained control, but <xref:Microsoft.AspNetCore.Components.ComponentBase.ShouldRender%2A> can be used to selectively render a component responding to a UI event. Using <xref:Microsoft.AspNetCore.Components.ComponentBase.ShouldRender%2A> might also be important in scenarios where a large number of components are rendered. Consider a grid, where use of <xref:Microsoft.AspNetCore.Components.EventCallback> in one component in one cell of the grid calls <xref:Microsoft.AspNetCore.Components.ComponentBase.StateHasChanged%2A> on the grid. Calling <xref:Microsoft.AspNetCore.Components.ComponentBase.StateHasChanged%2A> causes a re-render of every child component. If only a small number of cells require rerendering, use <xref:Microsoft.AspNetCore.Components.ComponentBase.ShouldRender%2A> to avoid the performance penalty of unnecessary renders.
 
 In the following example: