MVC WebGrid如何更新查询字符串

Question

When you enable paging and sorting on MVC's WebGrid, it automatically appends sort and page parameters in the query string automatically. How does it do that? I understand how it creates a link for page n, but how does if read the query string to know what page to produce?

What really confuses me is that, in the controller, I don't have to specify the page and sort parameters, but they work anyway. What manner of witchcraft is this?

in case I wasn't clear enough,

here is the gridview definition

@{ var grid = new WebGrid(Model.Customers, rowsPerPage: 25, canPage: true }); }

here is the query string that is produced:

/Customer?sort=Notes&sortdir=ASC

and my Customer.Index controller

//no parameters here. how does WebGrid maintain querystring?
public ActionResult Index() 
{
    ...
}

Answer 1

Long story short, it just plucks the values from HttpContext.Request.QueryString , which is not that magical afterall.

For example, here's where it accesses the sort field:

    public string SortColumn {
        get { 
            if (!_sortColumnSet) { 
                string sortColumn = QueryString[SortFieldName];
                // blah blah blah
            } 
            // blah blah blah
            return _sortColumn;
        } 
        set {
            // blah blah blah omitted for brevity
        } 
    }