Why HttpContext?

[Jason Madison]

I have been reading some asp.net code and wondered why it uses HttpContext.

On one page this is done:

// ------------------------------------------------------------------------
HttpContext ctx = HttpContext.Current;
string chartID = Guid.NewGuid ().ToString ();

ctx.Session [chartID] = byteArr;
imgHondaLineup.ImageUrl = string.Concat ("chart.ashx?", chartID);

then in the code behind the chart.ashx page this is done:

public void ProcessRequest (HttpContext ctx)
{
string chartID = ctx.Request.QueryString[0];
Array arr = (Array) ctx.Session [chartID];
....
ctx.Response.ContentType = "image/png";
ctx.Response.StatusCode = 200;
ctx.Response.End ();

What I want to understand is what would be the difference if the HttpContext
instance wasn't used. E.g.

Session [chartID] = byteArr;

....
string chartID = Request.QueryString[0];
Array arr = (Array) Session [chartID];
....
....
Response.ContentType = "image/png";
Response.StatusCode = 200;

etc.

Thanks

 

[Brock Allen]

These APIs like Request, Response, Session, etc, are made available to the
current scope typically as a property you've inherited from a base class
(like Page, or Control). In some contexts there is no base class that has
made those objects available, so the static HttpContext.Current property
is another way to acces those objects. It makes all the info about the current
HTTP request available.