Blazor snippet samp and NRT work

aspnetcore/blazor/call-web-api.md

@@ -40,7 +40,7 @@ Use the following `TodoItem` class with this article's examples if you build the
 public class TodoItem
 {
     public long Id { get; set; }
-    public string Name { get; set; }
+    public string? Name { get; set; }
     public bool IsComplete { get; set; }
 }
 ```
@@ -109,7 +109,7 @@ else
 }
 
 @code {
-    private TodoItem[] todoItems;
+    private TodoItem[]? todoItems;
 
     protected override async Task OnInitializedAsync() => 
         todoItems = await Http.GetFromJsonAsync<TodoItem[]>("api/TodoItems");
@@ -132,7 +132,7 @@ In the following component code, `newItemName` is provided by a bound element of
 <button @onclick="AddItem">Add</button>
 
 @code {
-    private string newItemName;
+    private string? newItemName;
 
     private async Task AddItem()
     {
@@ -152,7 +152,7 @@ var content = await response.Content.ReadFromJsonAsync<WeatherForecast>();
 
 <xref:System.Net.Http.Json.HttpClientJsonExtensions.PutAsJsonAsync%2A> sends an HTTP PUT request with JSON-encoded content.
 
-In the following component code, `editItem` values for `Name` and `IsCompleted` are provided by bound elements of the component. The item's `Id` is set when the item is selected in another part of the UI (not shown) and `EditItem` is called. The `SaveItem` method is triggered by selecting the `<button>` element.
+In the following component code, `editItem` values for `Name` and `IsCompleted` are provided by bound elements of the component. The item's `Id` is set when the item is selected in another part of the UI (not shown) and `EditItem` is called. The `SaveItem` method is triggered by selecting the `<button>` element. Note that the following example doesn't show loading `todoItems` for brevity (see the [GET from JSON (`GetFromJsonAsync`)](#get-from-json-getfromjsonasync) section for an example of loading items).
 
 ```razor
 @using System.Net.Http
@@ -165,7 +165,7 @@ In the following component code, `editItem` values for `Name` and `IsCompleted`
 <button @onclick="SaveItem">Save</button>
 
 @code {
-    private string id;
+    private string? id;
     private TodoItem editItem = new TodoItem();
 
     private void EditItem(long id)
@@ -258,7 +258,7 @@ else
 }
 
 @code {
-    private WeatherForecast[] forecasts;
+    private WeatherForecast[]? forecasts;
 
     protected override async Task OnInitializedAsync()
     {
@@ -351,7 +351,7 @@ else
 }
 
 @code {
-    private WeatherForecast[] forecasts;
+    private WeatherForecast[]? forecasts;
 
     protected override async Task OnInitializedAsync()
     {
@@ -456,8 +456,8 @@ else
 </p>
 
 @code {
-    private WeatherForecast[] forecasts;
-    private string exceptionMessage;
+    private WeatherForecast[]? forecasts;
+    private string? exceptionMessage;
 
     protected override async Task OnInitializedAsync()
     {

aspnetcore/blazor/components/cascading-values-and-parameters.md

@@ -60,26 +60,22 @@ In the following example, two [`CascadingValue`](xref:Microsoft.AspNetCore.Compo
 </CascadingValue>
 
 @code {
-    private CascadingType parentCascadeParameter1;
+    private CascadingType? parentCascadeParameter1;
 
     [Parameter]
-    public CascadingType ParentCascadeParameter2 { get; set; }
-
-    ...
+    public CascadingType? ParentCascadeParameter2 { get; set; }
 }
 ```
 
 In a descendant component, the cascaded parameters receive their cascaded values from the ancestor component by <xref:Microsoft.AspNetCore.Components.CascadingValue%601.Name%2A>:
 
 ```razor
-...
-
 @code {
     [CascadingParameter(Name = "CascadeParam1")]
-    protected CascadingType ChildCascadeParameter1 { get; set; }
+    protected CascadingType? ChildCascadeParameter1 { get; set; }
 
     [CascadingParameter(Name = "CascadeParam2")]
-    protected CascadingType ChildCascadeParameter2 { get; set; }
+    protected CascadingType? ChildCascadeParameter2 { get; set; }
 }
 ```
 
@@ -131,13 +127,13 @@ Child `Tab` components aren't explicitly passed as parameters to the `TabSet`. I
 
 @code {
     [Parameter]
-    public RenderFragment ChildContent { get; set; }
+    public RenderFragment? ChildContent { get; set; }
 
-    public ITab ActiveTab { get; private set; }
+    public ITab? ActiveTab { get; private set; }
 
     public void AddTab(ITab tab)
     {
-        if (ActiveTab == null)
+        if (ActiveTab is null)
         {
             SetActiveTab(tab);
         }
@@ -170,25 +166,25 @@ Descendent `Tab` components capture the containing `TabSet` as a cascading param
 
 @code {
     [CascadingParameter]
-    public TabSet ContainerTabSet { get; set; }
+    public TabSet? ContainerTabSet { get; set; }
 
     [Parameter]
-    public string Title { get; set; }
+    public string? Title { get; set; }
 
     [Parameter]
-    public RenderFragment ChildContent { get; set; }
+    public RenderFragment? ChildContent { get; set; }
 
-    private string TitleCssClass => 
-        ContainerTabSet.ActiveTab == this ? "active" : null;
+    private string? TitleCssClass => 
+        ContainerTabSet?.ActiveTab == this ? "active" : null;
 
     protected override void OnInitialized()
     {
-        ContainerTabSet.AddTab(this);
+        ContainerTabSet?.AddTab(this);
     }
 
     private void ActivateTab()
     {
-        ContainerTabSet.SetActiveTab(this);
+        ContainerTabSet?.SetActiveTab(this);
     }
 }
 ```

aspnetcore/blazor/components/class-libraries.md

@@ -340,6 +340,10 @@ Blazor WebAssembly and RCL projects *automatically* enable browser compatibility
 When authoring a library, indicate that a particular API isn't supported in browsers by specifying `browser` to <xref:System.Runtime.Versioning.UnsupportedOSPlatformAttribute>:
 
 ```csharp
+using System.Runtime.Versioning;
+
+...
+
 [UnsupportedOSPlatform("browser")]
 private static string GetLoggingDirectory()
 {

aspnetcore/blazor/components/control-head-content.md

@@ -23,30 +23,7 @@ The following example sets the page's title and description using Razor.
 
 `Pages/ControlHeadContent.razor`:
 
-```razor
-@page "/control-head-content"
-
-<h1>Control &lt;head&gt; content</h1>
-
-<p>
-    Title: @title
-</p>
-
-<p>
-    Description: @description
-</p>
-
-<PageTitle>@title</PageTitle>
-
-<HeadContent>
-    <meta name="description" content="@description">
-</HeadContent>
-
-@code {
-    private string description = "Description set by component";
-    private string title = "Title set by component";
-}
-```
+[!code-razor[](~/blazor/samples/6.0/BlazorSample_WebAssembly/Pages/control-head-content/ControlHeadContent.razor?highlight=13,15-17)]
 
 ## Control head content during prerendering
 

aspnetcore/blazor/components/data-binding.md

@@ -98,7 +98,10 @@ Binding supports [`multiple`](https://developer.mozilla.org/docs/Web/HTML/Attrib
 
     void SelectedCarsChanged(ChangeEventArgs e)
     {
-        SelectedCars = (string[])e.Value;
+        if (e.Value is not null)
+        {
+            SelectedCars = (string[])e.Value;
+        }
     }
 }
 ```