使用ASP.NET，检查以下url查询字符串中的foo参数的正确方法是什么？ 这是否可能？
http://example.com?bar=3&foo
我已经尝试检查Request ["foo"] 以及Request.QueryString ["foo"] ，但两者都得到null。 我还尝试使用 QueryString 集合中的值填充一个 List ，但正如我在下面提到的那样，它不包括该值。
我明白 Request["foo"] 没有值，但它不应该返回空字符串而不是null吗？即使没有值，是否有办法找出查询字符串键是否存在？
我在这里发现，Request.QueryString.AllKeys在空的查询字符串参数中包括null。
正如James和Dreas所述，使用正则表达式解析原始URL可能是最好（也可能是唯一）的方法。
Regex.IsMatch(Request.RawUrl, "[?&]thumb([&=]|$)")
You can use null as the key for the NameValueCollection and it will give you a comma-delimited list of parameter names that don t have values.
For http://example.com?bar=3&foo you would use Request.QueryString[null] and it would retrieve foo.
If you have more than one parameter name without a value, it will give you a value that is comma-delimited.
For http://example.com?bar=3&foo&test you would get foo,test as a value back.
Update:
You can actually use Request.QueryString.GetValues(null) to get the parameter names that don t have values.
Request.ServerVariables["QUERY_STRING"] will return the query string, complete, as a string. Then search it using a Regex or IndexOf
You get null because the foo parameter doesn t have a value with it.
...What s the problem exactly?
If you still want to check for its existence (although it lacks a value), try something like this:
bool doesFooExist = Request.Url.AbsoluteUri.IndexOf("foo=") >= 0 ? true : false;
Dreas is correct. Variable "bar" has a value but foo does not.
QueryString["Bar"] will return 3 because it has the value 3 associated with the variable Bar. However, Foo will return null because their is no value and when you are calling QueryString on a variable or key, you are querying for the value, not the key, so that is why you are returning null.
query string is probably a waste one. If you use Request.Params[""] or iterate it, then you will find your desired one. Its really handy than other things.
Let me know if you need any help in this.