When do Request.Params and Request.Form differ?

Question

I recently encountered a problem where a value was null if accessed with Request.Form but fine if retrieved with Request.Params. What are the differences between these meth

Answer 1

Request.Form only includes variables posted through a form, while Request.Params includes both posted form variables and get variables specified as URL parameters.

Answer 2

The reason was that the value I was retrieving was from a form element, but the submit was done through a link + JQuery, not through a form button submit.

Answer 3

Request.Params contains a combination of QueryString, Form, Cookies and ServerVariables (added in that order).

The difference is that if you have a form variable called "key1" that is in both the QueryString and Form then Request.Params["key1"] will return the QueryString value and Request.Params.GetValues("key1") will return an array of [querystring-value, form-value].

If there are multiple form values or cookies with the same key then those values will be added to the array returned by GetValues (ie. GetValues will not return a jagged array)