Difference between Request.Form and Request.QueryString?

Question 1

In Request.Form the data is posted in the http request body whereas in QueryString data is sent through url.

Question 2

I found some other difference

Request("id")

will first try to locate

Request.Form("id")

then

Request.Querystring("id")

then

Request.Cookies("id")

and finally

Request.ServerVariables("id")

it is reccommended to use the explicit naming convention if possible because it is more efficient and more readable.it also enables you to be sure where your information is coming from since the system will stop after the first hit is made.... It is also faster for the system if you specify the location of the information.

and we can refer this link for more some details :

http://www.hanselman.com/blog/ASPNETParamsCollectionVsQueryStringFormsVsRequestindexAndDoubleDecoding.aspx

But any one know any other difference, I really appreciate that .

Question 3

As stated on MSDN,

(Request.Form): The value of Request.Form(element) is an array of all the values of element that occur in the request body. You can determine the number of values of a parameter by calling Request.Form(element).Count. If a parameter does not have multiple values associated with it, the count is 1. If the parameter is not found, the count is 0.

and (Request.QueryString): The value of Request.QueryString(parameter) is an array of all of the values of parameter that occur in QUERY_STRING. You can determine the number of values of a parameter by calling Request.QueryString(parameter).Count. If a variable does not have multiple data sets associated with it, the count is 1. If the variable is not found, the count is 0.

So, some things to note:

In a typical Form on a page, we may include some hidden elements:

<form method="post">
   <input type="hidden" name="lol" value="cat" />
   <input type="text" />
</form>

Hidden elements (if memory serves), are not displayed in the QueryString. So, I would assume that there are some things that are not shown in Request.QueryString. Unfortunately I am in the process of re-installing dev apps on a new machine and cannot test this at the moment but if I'm right, when you POST a form, more details about the form and its contents gets sent. And when you access QueryString, you are only seeing the things that make up the entirety of the URL, e.g.:

http://somesite.com/index.html?v=1&NonHiddenElement=lol&ManualValue=hello

Question 4

Request.Form - means you are wanting to retrieve the values for the form that was posted.

Request.QueryString - means you are wanting to retrieve values that have been passed on the querystring.

Question 5

Request.Form()

The Form collection retrieves the values of form elements posted to the HTTP request body, Only those elements and value which exist in your Form.

Request.QueryString()

The QueryString collection retrieves the values of the variables in the HTTP query string, Here you can append any of your custom variable and value which event dose not exist in your Form.

Question 6

Request.Form Collection

The Form collection retrieves the values of form elements posted to the HTTP request body, with a form using the POST method.
Form input is contained in headers. It is wise to not trust the data that is contained in headers, as this information can be falsified by malicious users. For example, do not rely on data such as cookies to securely identify a user.
As a security precaution, always encode header data or user input before using it. A general method of encoding data is to use Server.HTMLEncode. Alternatively, you can validate header data and user input with a short function such as the one described in Validating User Input to Avoid Attacks. For more detailed information about developing secure Web applications, see chapter 12 of MS Press - Writing Secure Code.
Syntax
Request.Form(element)[(index)|.Count]
Parameters
element
The name of the form element from which the collection is to retrieve values.
index
An optional parameter that enables you to access one of multiple values for a parameter. It can be any integer in the range 1 to Request.Form(parameter).Count.
Applies To
Request Object
Remarks
The Form collection is indexed by the names of the parameters in the request body. The value of Request.Form(element) is an array of all the values of element that occur in the request body. You can determine the number of values of a parameter by calling Request.Form(element).Count. If a parameter does not have multiple values associated with it, the count is 1. If the parameter is not found, the count is 0.
To reference a single value of a form element that has multiple values, you must specify a value for the index parameter. The index parameter may be any number between 1 and Request.Form(element).Count. If you reference one of multiple form parameters without specifying a value for index, the data is returned as a comma-delimited string.
When you use parameters with Request.Form, the Web server parses the HTTP request body and returns the specified data. If your application requires unparsed data from the form, you can access it by calling Request.Form without any parameters.

Request.QueryString Collection

The QueryString collection retrieves the values of the variables in the HTTP query string. The HTTP query string is specified by the values following the question mark (?). Several different processes can generate a query string. For example, the following anchor tag generates a variable named string with the value "this is a sample."
<A HREF="example.asp?string=this is a sample">string sample</A>

Query strings are also generated by sending a form or by a user typing a query into the address box of the browser.
Query strings are contained in request headers. It is wise to not trust the data that is contained in headers, as this information can be falsified by malicious users. For example, do not rely on data such as cookies to securely identify a user.
As a security precaution, always encode header data or user input before using it. A general method of encoding data is to use Server.HTMLEncode. Alternatively, you can validate header data and user input with a short function such as the one described in Validating User Input to Avoid Attacks. For more detailed information about developing secure Web applications, see chapter 12 of MS Press - Writing Secure Code.
Syntax
Request.QueryString(variable)[(index)|.Count]
Parameters
variable
Specifies the name of the variable in the HTTP query string to retrieve.
index
An optional parameter that enables you to retrieve one of multiple values for variable. It can be any integer value in the range 1 to Request.QueryString(variable).Count.
Applies To
Request Object
Remarks
The QueryString collection is a parsed version of the QUERY_STRING variable in the ServerVariables collection. It enables you to retrieve the QUERY_STRING variable by name. The value of Request.QueryString(parameter) is an array of all of the values of parameter that occur in QUERY_STRING. You can determine the number of values of a parameter by calling Request.QueryString(parameter).Count. If a variable does not have multiple data sets associated with it, the count is 1. If the variable is not found, the count is 0.
To reference a QueryString variable in one of multiple data sets, you specify a value for index. The index parameter can be any value between 1 and Request.QueryString(variable).Count. If you reference one of multiple QueryString variables without specifying a value for index, the data is returned as a comma-delimited string.
When you use parameters with Request.QueryString, the server parses the parameters sent to the request and returns the specified data. If your application requires unparsed QueryString data, you can retrieve it by calling Request.QueryString without any parameters.
You can use an iterator to loop through all the data values in a query string.

For example, if the following request is sent:

for more details click this link