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Welcome to this week’s edition of ProgrammingPro!

In today’sExpert Insight, we bring you an excerpt from the recently published book, C# 13 and .NET 9 – Modern Cross-Platform Development Fundamentals - Ninth Edition, which demonstrates defining routable page components, passing route parameters, and navigating routes in Blazor.

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Here’s an excerpt from “Chapter 14: Building Interactive Web Components Using Blazor" in the book, C# 13 and .NET 9 – Modern Cross-Platform Development Fundamentals - Ninth Edition by Mark J. Price, published in November 2024.

To create a routable page component, add the@pagedirective to the top of a component’s.razorfile, as shown in the following markup:

@page "/customers"

The preceding code is the equivalent of a mapped endpoint inProgram.cs, as shown in the following code:

app.MapGet("/customers", () => ...);

TheRoutercomponent scans the assembly specifically in itsAppAssemblyparameter for Blazor components with the@pagedirective, registering their URL paths as endpoints.

At runtime, a page component is merged with any specific layout that you have specified in theRoutes.razorfile<RouteView>component. By default, the Blazor Web App project template definesMainLayout.razoras the layout for page components.

Pro Tip:

Good Practice: By convention, put routable page Blazor components in theComponents\Pagesfolder.

Microsoft provides a dependency service namedNavigationManagerthat understands Blazor routing and theNavLinkcomponent. TheNavigateTomethod is used to go to the specified URL.

Blazor routes can include case-insensitive named parameters, and your code can most easily access the values passed by binding the parameter to a property in the code block, using the[Parameter]attribute, as shown in the following markup:

@page "/customers/{country}"
<div>Country parameter as the value: @Country</div>
@code {
[Parameter]
public string Country { get; set; }
}

The recommended way to handle a parameter that should have a default value when it is missing is to suffix the parameter with?and use the null-coalescing operator in theOnParametersSetmethod, as shown in the following markup:

@page "/customers/{country?}"
<div>Country parameter as the value: @Country</div>
@code {
[Parameter]
public string Country { get; set; }
protected override void OnParametersSet()
{
// If the automatically set property is null, then
// set its value to USA.
Country = Country ?? "USA";
}
}

C# 13 and .NET 9 – Modern Cross-Platform Development Fundamentals - Ninth Editionwas published in Novemver 2024. Packt library subscribers can continue reading the entire book for free or you can buy the book