Bound field or property expression convention

aspnetcore/blazor/components/data-binding.md

@@ -892,6 +892,76 @@ In the following `NestedChild` component, the `NestedGrandchild` component:
 
 For an alternative approach suited to sharing data in memory and across components that aren't necessarily nested, see <xref:blazor/state-management>.
 
+## Bound field or property expression tree
+
+A bound field or property's [expression tree](/dotnet/csharp/advanced-topics/expression-trees/) is obtained by adding a property named for the field or property (`{PARAMETER OR FIELD NAME}Expression`).
+
+The following `ChildParameterExpression` component identifies the `Year` expression's model and field name. A <xref:Microsoft.AspNetCore.Components.Forms.FieldIdentifier>, which is used to obtain the model and field name, uniquely identifies a single field that can be edited. This may correspond to a property on a model object or can be any other named value. Use of a parameter's expression is useful when creating custom validation components, which isn't covered by the Microsoft Blazor documentation but is addressed by numerous third-party resources.
+
+`ChildParameterExpression.razor`:
+
+:::moniker range=">= aspnetcore-8.0"
+
+:::code language="razor" source="~/../blazor-samples/8.0/BlazorSample_BlazorWebApp/Components/ChildParameterExpression.razor":::
+
+:::moniker-end
+
+:::moniker range=">= aspnetcore-7.0 < aspnetcore-8.0"
+
+:::code language="razor" source="~/../blazor-samples/7.0/BlazorSample_WebAssembly/Shared/data-binding/ChildParameterExpression.razor":::
+
+:::moniker-end
+
+:::moniker range=">= aspnetcore-6.0 < aspnetcore-7.0"
+
+:::code language="razor" source="~/../blazor-samples/6.0/BlazorSample_WebAssembly/Shared/data-binding/ChildParameterExpression.razor":::
+
+:::moniker-end
+
+:::moniker range=">= aspnetcore-5.0 < aspnetcore-6.0"
+
+:::code language="razor" source="~/../blazor-samples/5.0/BlazorSample_WebAssembly/Shared/data-binding/ChildParameterExpression.razor":::
+
+:::moniker-end
+
+:::moniker range="< aspnetcore-5.0"
+
+:::code language="razor" source="~/../blazor-samples/3.1/BlazorSample_WebAssembly/Shared/data-binding/ChildParameterExpression.razor":::
+
+:::moniker-end
+
+`Parent3.razor`:
+
+:::moniker range=">= aspnetcore-8.0"
+
+:::code language="razor" source="~/../blazor-samples/8.0/BlazorSample_BlazorWebApp/Components/Pages/Parent3.razor":::
+
+:::moniker-end
+
+:::moniker range=">= aspnetcore-7.0 < aspnetcore-8.0"
+
+:::code language="razor" source="~/../blazor-samples/7.0/BlazorSample_WebAssembly/Pages/data-binding/Parent3.razor":::
+
+:::moniker-end
+
+:::moniker range=">= aspnetcore-6.0 < aspnetcore-7.0"
+
+:::code language="razor" source="~/../blazor-samples/6.0/BlazorSample_WebAssembly/Pages/data-binding/Parent3.razor":::
+
+:::moniker-end
+
+:::moniker range=">= aspnetcore-5.0 < aspnetcore-6.0"
+
+:::code language="razor" source="~/../blazor-samples/5.0/BlazorSample_WebAssembly/Pages/data-binding/Parent3.razor":::
+
+:::moniker-end
+
+:::moniker range="< aspnetcore-5.0"
+
+:::code language="razor" source="~/../blazor-samples/3.1/BlazorSample_WebAssembly/Pages/data-binding/Parent3.razor":::
+
+:::moniker-end
+
 ## Additional resources
 
 * [Parameter change detection and additional guidance on Razor component rendering](xref:blazor/components/rendering)