InvalidOperationException: The relative page path 'Test' can only be used while executing a Razor Page. Specify a root relative path with a leading '/' to generate a URL outside of a Razor Page. If you are using LinkGenerator then you must provide the current HttpContext to use relative pages.

InvalidOperationException: The relative page path 'Test' can only be used while executing a Razor Page. Specify a root relative path with a leading '/' to generate a URL outside of a Razor Page. If you are using LinkGenerator then you must provide the current HttpContext to use relative pages.

When working with ASP.NET Core web applications, it is important to understand how to generate URLs for different types of pages in your application. One common scenario is when you want to create a link to a page that is not a Razor Page, such as an API endpoint or a static file. In this case, you can use the `LinkGenerator` class to generate a URL that takes into account the current HTTP context and any relative paths specified in your application.

The `LinkGenerator` class provides several methods for generating URLs, including `CreateHref`, `CreatePath`, and `CreateAbsoluteUri`. These methods allow you to specify the type of URL you want to generate, as well as any parameters or query strings that should be included in the URL.

For example, if you have an API endpoint that you want to link to from your application, you can use the `CreateHref` method to generate a relative URL that takes into account the current HTTP context

csharp
var apiUrl = new Uri(Request.Scheme + "
//" + Request.Host + "/api/endpoint");
var linkGenerator = new LinkGenerator(apiUrl);
var href = linkGenerator.CreateHref("endpoint");

In this example, the `CreateHref` method is used to generate a relative URL for the endpoint with the name "endpoint". The resulting URL will be in the format of "//localhost
5000/api/endpoint>" if you are running your application on localhost.

If you want to generate an absolute URL, you can use the `CreateAbsoluteUri` method instead

csharp
var apiUrl = new Uri(Request.Scheme + "
//" + Request.Host + "/api/endpoint");
var linkGenerator = new LinkGenerator(apiUrl);
var uri = linkGenerator.CreateAbsoluteUri("endpoint");

In this example, the `CreateAbsoluteUri` method is used to generate an absolute URL for the endpoint with the name "endpoint". The resulting URL will be in the format of "//localhost
5000/api/endpoint>" if you are running your application on localhost.

It's important to note that when using `LinkGenerator`, you need to provide the current HTTP context by passing it as a parameter to the constructor. This allows the `LinkGenerator` to take into account the scheme, host, and path of the current request and generate URLs that are relative to the current location in your application.

Another scenario where you might want to use `LinkGenerator` is when working with static files such as images or CSS files. In this case, you can use the `CreatePath` method to generate a relative path for the file

csharp
var imageUrl = new Uri(Request.Scheme + "
//" + Request.Host + "/images/image.jpg");
var linkGenerator = new LinkGenerator(imageUrl);
var path = linkGenerator.CreatePath("image.jpg");

In this example, the `CreatePath` method is used to generate a relative path for an image file with the name "image.jpg". The resulting URL will be in the format of "//localhost
5000/images/image.jpg>" if you are running your application on localhost.

It's important to note that when using `LinkGenerator` with static files, you need to make sure that the file is located in the correct directory relative to the current request. For example, if the image file is located in a subdirectory called "images" under the root directory of your application, you will need to specify the full path to the file when creating the `Uri` object.

In summary, `LinkGenerator` is a powerful tool for generating URLs in ASP.NET Core web applications. It allows you to generate relative and absolute URLs that take into account the current HTTP context and any relative paths specified in your application. By using `LinkGenerator`, you can easily create links to different types of pages in your application, including API endpoints, static files, and more.