If I call
var nvc = HttpUtility.ParseQueryString("?foo=bar&baz=robots")
I get back a NameValueCollection where if I call ToString on it, I get back a query string.
var str = nvc.ToString(); //foo=bar&baz=robots....
If I create a new NameValueCollection, add stuff to it, and call ToString() on it, I don't get back a query string.
var nvc= new NameValueCollection();
nvc["foo"] = "bar";
var str = nvc.ToString(); //default for Object.ToString()
Also there doesn't seem to be a way to construct a NameValueCollection that acts as a query string editor. Is there one? If not, why? Being able to edit query strings is a pretty useful thing, but this functionality is totally hidden away in an obscure mode of some object most people don't even know exists.
This is done by the internal HttpValueCollection class, which inherits NameValueCollection and overrides ToString().
ParseQueryString() is the only public way to construct this class.
In the end, query strings are meant to be very simple. So, you can just do something like this:
Dictionary<string, string> dict = new Dictionary<string, string>();
dict.Add("somekey", "someval");
var querystring = string.Join("&", dict.Select(kv => HttpUtility.UrlEncode(kv.Key) + "=" + HttpUtility.UrlEncode(kv.Value)));
Completely untested of course. But yeah, a query string is name=value separated by ampersands. Is there something else you need to do?
Related
I have a query string that looks something like this:
"somename1=123&QueryString=PlaceHolder%3dNothing%26anotherid%3dsomevalue&somename=somevalue"
but I want the query string to be something like the query string below and replace the whole query string with the updated one is there any way to do that without redirection?
"somename1=somevalue1&PlaceHolder=Nothing&somename2=somevalue2&somename3=somevalue3"
basically need to remove:
"QueryString=" with empty string
"%3d" with "&"
"%26" with "="
So far I've done is:
string strQueryString = Request.QueryString.ToString();
if (strQueryString.Contains("QueryString="))
{
strQueryString = strQueryString.Replace("QueryString=", "");
if (strQueryString.Contains("%26")) strQueryString = strQueryString.Replace("%26", "&");
if (strQueryString.Contains("%3d")) strQueryString = strQueryString.Replace("%3d", "=");
string x = strQueryString;
}
and:
// reflect to readonly property
PropertyInfo isreadonly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic);
// make collection editable
isreadonly.SetValue(this.Request.QueryString, false, null);
if (this.Request.QueryString.ToString().Contains("QueryString="))
{
this.Request.QueryString.ToString().Replace("QueryString=", "");
if (this.Request.QueryString.ToString().Contains("%26")) this.Request.QueryString.ToString().Replace("%26", "&");
if (this.Request.QueryString.ToString().Contains("%3d")) this.Request.QueryString.ToString().Replace("%3d", "=");
string x = this.Request.QueryString.ToString();
}
// make collection readonly again
isreadonly.SetValue(this.Request.QueryString, true, null);
The second part of the code is not replacing the characters and I don't know how after removing all character or replacing them change the query string to new query string.
Any help is greatly appreciated.
Changing the query string of the current request is not supported. Using private Reflection to edit some in-memory state will most likely break ASP.NET because it assumes that the query string is immutable. The only way to change the query string is to issue a new request, either by doing a redirect, or by doing a sort of sub-request, such as by making a new HTTP request to the same page but with a different query string.
May I suggest a not very well known built in key/value dictionary, Context.Items.
With this you very like get a better performance than toggle the readonly QueryString object, and it also last throughout a request so you can share it between module, handlers, etc.
Create
string strQueryString = Request.QueryString.ToString();
if (strQueryString.Contains("QueryString="))
{
HttpContext.Current.Items("qs") = strQueryString.Replace("QueryString=", "").Replace("%26", "&").Replace("%3d", "=");
}
Use
string x = HttpContext.Current.Items("qs_d").ToString();
Side note: I shortened you code some, as there is no need to first check if anything contains and if so, replace, just run replace, it will be faster
how can i modified the querystring?
I have capture the query string like this
qs = Request.QueryString["flag"].ToString();
and then rebuilt the query string with modified values
and response.redirect(url & qs) to it
While I'm not sure I'd suggest using this approach liberally, if you wanted to reconstruct the path and query string with a few changes... you could convert the query string to an editable collection, modify it, then rebuild it from your new collection.
Goofy example...
// create dictionary (editable collection) of querystring
var qs = Request.QueryString.AllKeys
.ToDictionary(k => k, k => Request.QueryString[k]);
// modify querystring
qs["flag"] = "2";
// rebuild querystring
var redir = string.Format("{0}{1}", Request.Path,
qs.Aggregate(new StringBuilder(),
(sb, arg) => sb.AppendFormat("{0}{1}={2}",
sb.Length > 0 ? "&" : "?", arg.Key, arg.Value)));
// do something with it
Response.Redirect(redir);
While I definitely wouldn't recommend the below for production code, for testing purposes you can use reflection to make the querystring collection editable.
// Get the protected "IsReadOnly" property of the collection
System.Reflection.PropertyInfo prop = Request.QueryString.GetType()
.GetProperty("IsReadOnly", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
// Set the property false (writable)
prop.SetValue(Request.QueryString, false, null);
// Have your way with it.
Request.QueryString.Add("flag", "2");
To combine the required destination URL based on the Request’s properties, use something like this:
string destUrl = string.Format("{0}://{1}{2}/", Request.Url.Scheme, Request.Url.Authority, Request.Url.AbsolutePath);
if (destUrl.EndsWith("/"))
destUrl = destUrl.TrimEnd(new char[] { '/' });
if (!string.IsNullOrEmpty(Request.QueryString["paramName"])) {
destUrl = string.Format("{0}?paramName={1}", destUrl, "paramValueHere");
Response.Redirect(destUrl);
}
i am not sure if I understand your question. You can just alter the string qs and use.
qs = qs + "modification"
Response.Redirect("this.aspx?flag=" + qs )
The stuff in the Request class deals with the request that got you to the page. You can't edit it because the client constructed it, not the server.
I have an ASP.NET page which takes a number of parameters in the query string:
search.aspx?q=123&source=WebSearch
This would display the first page of search results. Now within the rendering of that page, I want to display a set of links that allow the user to jump to different pages within the search results. I can do this simply by append &page=1 or &page=2 etc.
Where it gets complicated is that I want to preserve the input query string from the original page for every parameter except the one that I'm trying to change. There may be other parameters in the url used by other components and the value I'm trying to replace may or may not already be defined:
search.aspx?q=123&source=WebSearch&page=1&Theme=Blue
In this case to generate a link to the next page of results, I want to change page=1 to page=2 while leaving the rest of the query string unchanged.
Is there a builtin way to do this, or do I need to do all of the string parsing/recombining manually?
You can't modify the QueryString directly as it is readonly. You will need to get the values, modify them, then put them back together. Try this:
var nameValues = HttpUtility.ParseQueryString(Request.QueryString.ToString());
nameValues.Set("page", "2");
string url = Request.Url.AbsolutePath;
string updatedQueryString = "?" + nameValues.ToString();
Response.Redirect(url + updatedQueryString);
The ParseQueryString method returns a NameValueCollection (actually it really returns a HttpValueCollection which encodes the results, as I mention in an answer to another question). You can then use the Set method to update a value. You can also use the Add method to add a new one, or Remove to remove a value. Finally, calling ToString() on the name NameValueCollection returns the name value pairs in a name1=value1&name2=value2 querystring ready format. Once you have that append it to the URL and redirect.
Alternately, you can add a new key, or modify an existing one, using the indexer:
nameValues["temp"] = "hello!"; // add "temp" if it didn't exist
nameValues["temp"] = "hello, world!"; // overwrite "temp"
nameValues.Remove("temp"); // can't remove via indexer
You may need to add a using System.Collections.Specialized; to make use of the NameValueCollection class.
You can do this without all the overhead of redirection (which is not inconsiderable). My personal preference is to work with a NameValueCollection which a querystring really is, but using reflection:
// reflect to readonly property
PropertyInfo isReadOnly = typeof(System.Collections.Specialized.NameValueCollection).GetProperty("IsReadOnly", BindingFlags.Instance | BindingFlags.NonPublic);
// make collection editable
isReadOnly.SetValue(this.Request.QueryString, false, null);
// remove
this.Request.QueryString.Remove("foo");
// modify
this.Request.QueryString.Set("bar", "123");
// make collection readonly again
isReadOnly.SetValue(this.Request.QueryString, true, null);
Using this QueryStringBuilder helper class, you can grab the current QueryString and call the Add method to change an existing key/value pair...
//before: "?id=123&page=1&sessionId=ABC"
string newQueryString = QueryString.Current.Add("page", "2");
//after: "?id=123&page=2&sessionId=ABC"
Use the URIBuilder Specifically the link textQuery property
I believe that does what you need.
This is pretty arbitrary, in .NET Core at least. And it all boils down to asp-all-route-data
Consider the following trivial example (taken from the "paginator" view model I use in virtually every project):
public class SomeViewModel
{
public Dictionary<string, string> NextPageLink(IQueryCollection query)
{
/*
* NOTE: how you derive the "2" is fully up to you
*/
return ParseQueryCollection(query, "page", "2");
}
Dictionary<string, string> ParseQueryCollection(IQueryCollection query, string replacementKey, string replacementValue)
{
var dict = new Dictionary<string, string>()
{
{ replacementKey, replacementValue }
};
foreach (var q in query)
{
if (!string.Equals(q.Key, replacementKey, StringComparison.OrdinalIgnoreCase))
{
dict.Add(q.Key, q.Value);
}
}
return dict;
}
}
Then to use in your view, simply pass the method the current request query collection from Context.Request:
<a asp-all-route-data="#Model.NextPageLink(Context.Request.Query)">Next</a>
I want to dynamically populate a link with the URI of the current request, but set one specific query string parameter. All other querystring paramaters (if there are any) should be left untouched. And I don't know in advance what they might be.
Eg, imagine I want to build a link back to the current page, but with the querystring parameter "valueOfInterest" always set to be "wibble" (I'm doing this from the code-behind of an aspx page, .Net 3.5 in C# FWIW).
Eg, a request for either of these two:
/somepage.aspx
/somepage.aspx?valueOfInterest=sausages
would become:
/somepage.aspx?valueOfInterest=wibble
And most importantly (perhaps) a request for:
/somepage.aspx?boring=something
/somepage.aspx?boring=something&valueOfInterest=sausages
would preserve the boring params to become:
/somepage.aspx?boring=something&valueOfInterest=wibble
Caveats: I'd like to avoid string manipulation if there's something more elegant in asp.net that is more robust. However if there isn't something more elegant, so be it.
I've done (a little) homework:
I found a blog post which suggested copying the request into a local HttpRequest object, but that still has a read-only collection for the querystring params. I've also had a look at using a URI object, but that doesn't seem to have a querystring
This will work as long as [1] you have a valid URL to begin with (which seems reasonable) [2] you make sure that your new value ('sausages') is properly escaped. There's no parsing, the only string manipulation is to concatenate the parameters.
Edit
Here's the C#:
UriBuilder u = new UriBuilder(Request.Url);
NameValueCollection nv = new NameValueCollection(Request.QueryString);
/* A NameValueColllection automatically makes room if this is a new
name. You don't have to check for NULL.
*/
nv["valueOfInterest"] = "sausages";
/* Appending to u.Query doesn't quite work, it
overloaded to add an extra '?' each time. Have to
use StringBuilder instead.
*/
StringBuilder newQuery = new StringBuilder();
foreach (string k in nv.Keys)
newQuery.AppendFormat("&{0}={1}", k, nv[k]);
u.Query = newQuery.ToString();
Response.Redirect(u.Uri.ToString());
UriBuilder u = new UriBuilder(Request.Url);
NameValueCollection nv = new NameValueCollection(Request.QueryString);
nv["valueofinterest"] = "wibble";
string newQuery = "";
foreach (string k in nv.Keys)
{
newQuery += k + "=" + nv[k] + "&";
}
u.Query = newQuery.Substring(0,newQuery.Length-1);
Response.Redirect(u.ToString());
that should do it
If you can't find something that exists to do it, then build a bullet-proof function to do it that is thoroughly tested and can be relied upon. If this uses string manipulation, but is efficient and fully tested, then in reality it will be little different to what you may find any way.
I'm having some difficulty with using NVelocity in an ASP.NET MVC application. I'm using it as a way of generating emails.
As far as I can make out the details I'm passing are all correct, but it fails to load the template.
Here is the code:
private const string defaultTemplatePath = "Views\\EmailTemplates\\";
...
velocityEngine = new VelocityEngine();
basePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, defaultTemplatePath);
ExtendedProperties properties = new ExtendedProperties();
properties.Add(RuntimeConstants.RESOURCE_LOADER, "file");
properties.Add(RuntimeConstants.FILE_RESOURCE_LOADER_PATH, basePath);
velocityEngine.Init(properties);
The basePath is the correct directory, I've pasted the value into explorer to ensure it is correct.
if (!velocityEngine.TemplateExists(name))
throw new InvalidOperationException(string.Format("Could not find a template named '{0}'", name));
Template result = velocityEngine.GetTemplate(name);
'name' above is a valid filename in the folder defined as basePath above. However, TemplateExists returns false. If I comment that conditional out and let it fail on the GetTemplate method call the stack trace looks like this:
at NVelocity.Runtime.Resource.ResourceManagerImpl.LoadResource(String resourceName, ResourceType resourceType, String encoding)
at NVelocity.Runtime.Resource.ResourceManagerImpl.GetResource(String resourceName, ResourceType resourceType, String encoding)
at NVelocity.Runtime.RuntimeInstance.GetTemplate(String name, String encoding)
at NVelocity.Runtime.RuntimeInstance.GetTemplate(String name)
at NVelocity.App.VelocityEngine.GetTemplate(String name)
...
I'm now at a bit of an impasse. I feel that the answer is blindingly obvious, but I just can't seem to see it at the moment.
Have you considered using Castle's NVelocityTemplateEngine?
Download from the "TemplateEngine Component 1.1 - September 29th, 2009" section and reference the following assemblies:
using Castle.Components.Common.TemplateEngine.NVelocityTemplateEngine;
using Castle.Components.Common.TemplateEngine;
Then you can simply call:
using (var writer = new StringWriter())
{
_templateEngine.Process(data, string.Empty, writer, _templateContents);
return writer.ToString();
}
Where:
_templateEngine is your NVelocityTemplateEngine
data is your Dictionary of information (I'm using a Dictionary to enable me to access objects by a key ($objectKeyName) in my template.
_templateContents is the actual template string itself.
I hope this is of help to you!
Just to add, you'll want to put that into a static method returning a string of course!
Had this issue recently - NVelocity needs to be initialised with the location of the template files. In this case mergeValues is an anonymous type so in my template I can just refer to $Values.SomeItem:
private string Merge(Object mergeValues)
{
var velocity = new VelocityEngine();
var props = new ExtendedProperties();
props.AddProperty("file.resource.loader.path", #"D:\Path\To\Templates");
velocity.Init(props);
var template = velocity.GetTemplate("MailTemplate.vm");
var context = new VelocityContext();
context.Put("Values", mergeValues);
using (var writer = new StringWriter())
{
template.Merge(context, writer);
return writer.ToString();
}
}
Try setting the file.resource.loader.path
http://weblogs.asp.net/george_v_reilly/archive/2007/03/06/img-srchttpwwwcodegenerationnetlogosnveloc.aspx
Okay - So I'm managed to get something working but it is a bit of a hack and isn't anywhere near a solution that I want, but it got something working.
Basically, I manually load in the template into a string then pass that string to the velocityEngine.Evaluate() method which writes the result into the the given StringWriter. The side effect of this is that the #parse instructions in the template don't work because it still cannot find the files.
using (StringWriter writer = new StringWriter())
{
velocityEngine.Evaluate(context, writer, templateName, template);
return writer.ToString();
}
In the code above templateName is irrelevant as it isn't used. template is the string that contains the entire template that has been pre-loaded from disk.
I'd still appreciate any better solutions as I really don't like this.
The tests are the ultimate authority:
http://fisheye2.atlassian.com/browse/castleproject/NVelocity/trunk/src/NVelocity.Tests/Test/ParserTest.cs?r=6005#l122
Or you could use the TemplateEngine component which is a thin wrapper around NVelocity that makes things easier.