Cgi.request

Gets a request variable as a specific type, or the default value of it isn't there or isn't convertible to the request type.

Checks both GET and POST variables, preferring the POST variable, if available.

A nice trick is using the default value to choose the type:

/*
	The return value will match the type of the default.
	Here, I gave 10 as a default, so the return value will
	be an int.

	If the user-supplied value cannot be converted to the
	requested type, you will get the default value back.
*/
int a = cgi.request("number", 10);

if(cgi.get["number"] == "11")
	assert(a == 11); // conversion succeeds

if("number" !in cgi.get)
	assert(a == 10); // no value means you can't convert - give the default

if(cgi.get["number"] == "twelve")
	assert(a == 10); // conversion from string to int would fail, so we get the default

You can use an enum as an easy whitelist, too:

enum Operations {
	add, remove, query
}

auto op = cgi.request("op", Operations.query);

if(cgi.get["op"] == "add")
	assert(op == Operations.add);
if(cgi.get["op"] == "remove")
	assert(op == Operations.remove);
if(cgi.get["op"] == "query")
	assert(op == Operations.query);

if(cgi.get["op"] == "random string")
	assert(op == Operations.query); // the value can't be converted to the enum, so we get the default