How to read values from the querystring with ASP.NET Core?

I'm building one RESTful API using ASP.NET Core MVC and I want to use querystring parameters to specify filtering and paging on a resource that returns a collection.

In that case, I need to read the values passed in the querystring to filter and select the results to return.

I've already found out that inside the controller Get action accessing HttpContext.Request.Query returns one IQueryCollection.

The problem is that I don't know how it is used to retrieve the values. In truth, I thought the way to do was by using, for example

string page = HttpContext.Request.Query["page"]

The problem is that HttpContext.Request.Query["page"] doesn't return a string, but a StringValues.

Anyway, how does one use the IQueryCollection to actually read the querystring values?

Solution 1:

You can use [FromQuery] to bind a particular model to the querystring:

https://docs.microsoft.com/en-us/aspnet/core/mvc/models/model-binding

e.g.

[HttpGet()]
public IActionResult Get([FromQuery(Name = "page")] string page)
{...}

Solution 2:

You could use the ToString method on IQueryCollection which will return the desired value if a single page parameter is specified:

string page = HttpContext.Request.Query["page"].ToString();

if there are multiple values like ?page=1&page=2 then the result of the ToString call will be 1,2

But as @mike-g suggested in his answer you would better use model binding and not directly accessing the HttpContext.Request.Query object.