ASP.NET Core Razor page Handler, Basic concept

In ASP.NET Core Razor page, what is difference between OnGetSomeMethod and OnGet methods

In ASP.NET Core Razor Pages, methods like OnGet and OnGetSomeMethod follow a pattern that helps identify when and why specific handlers are triggered. Here’s the distinction between them:

1. OnGet Method

The OnGet method is the default handler that executes when a GET request is made to the page without any specific handler name in the query string or route.

This method is generally used to initialize data for the page or perform any action that’s required when the page first loads.

For example:

public void OnGet()
{
    // Initialization or data fetching logic
}

2. OnGetSomeMethod Method

OnGetSomeMethod is a named handler for GET requests and is executed when you explicitly specify handler=SomeMethod in the query string or route.

Named handlers are used when you want to handle different GET actions within the same Razor Page. For instance, OnGetChangedCountry might handle the logic needed when the user changes the country selection on the page, separate from the general page load handled by OnGet.

To call this handler, the request URL would need to include ?handler=SomeMethod (or it could be called from a form submission or JavaScript).

For example:

public void OnGetSomeMethod() // e.g. OnGetChangedCountry
{
    // Logic specific to changing the country, like loading cities for the selected country
}

Example Usage in a Razor Page

Here’s how you might set up and call the named handler in a Razor Page:

<form method="get">
    <select name="country" asp-page-handler="SomeMethod">
        <option value="USA">USA</option>
        <option value="Canada">Canada</option>
    </select>
    <button type="submit">Submit</button>
</form>

In this example:

When the form is submitted, the URL will include ?handler=SomeMethod, and OnGetSomeMethod will execute instead of OnGet.

Summary

• OnGet: Default GET request handler, used for general page initialization.
• OnGetSomeMethod: Named GET handler, used for specific actions like handling a country selection change on the page.
• Using named handlers allows for cleaner and more modular code when handling multiple GET actions on a single Razor Page.

Related links:

PageModel class

Directives in Razor Pages

MVC vs Razor Pages