Merge branch 'master' into release/3.0-preview9

Author: scottaddie

aspnetcore/blazor/forms-validation.md

@@ -199,3 +199,7 @@ The `ValidationMessage` component displays validation messages for a specific fi
 ```
 
 The `ValidationMessage` and `ValidationSummary` components support arbitrary attributes. Any attribute that doesn't match a component parameter is added to the generated `<div>` or `<ul>` element.
+
+### Validation of complex or collection type properties
+
+Validation attributes applied to the properties of a model validate when the form is submitted. However, the properties of collections or complex data types of a model aren't validated on form submission. To honor the nested validation attributes in this scenario, use a custom validation component. For an example, see the [Blazor Validation sample in the aspnet/samples GitHub repository](https://github.com/aspnet/samples/tree/master/samples/aspnetcore/blazor/Validation).