ASP.NET Key/Value List - asp.net

I'm doing a custom 404 page for a large website that's undergoing a redesign. There are about 40 high-use pages that customers may have bookmarked, and our new site structure will break these bookmarks.
On my custom 404 page, I want to alert them to the new URL if they attempt to navigate to one of these high-use pages via its old URL. So I have a couple of dynamic controls on the 404 page, one for a "did-you-want-this?" type of dialog, and another for a "if-so-go-here (and update your bookmark)" type of dialog. That's the easy part.
To suggest a new URL, I'm looking at the requested URL. If it has key words in it, I'm going to suggest the new URL based on that, and them I'm firing off the appropriate did-you-want..., and if-so... suggestions on the 404 page as mentioned above.
So I want to store these 40-ish key/value pairs (keyword/new-URL pairs) in a data structure, and I'm not sure what would be best. Dictionary? IDictionary? What's the difference and which is more appropriate?
Or am I totally on the wrong track?
Thanks for your time.

I would use the Dictionary<T,T> from the System.Collections.Generic namespace.

You could use NameValueCollection.

Maybe this is overkill for your use case, but I'd probably allow for multiple keywords per Uri, and a relative weight score. Then, dynamically score the keywords that match.
class UriSuggester {
private List<SuggestedUri> Uris { get; set; }
Uri[] GetSuggestions(Uri originalUri) {
var suggestionHits = new Dictionary<SuggestedUri, int>();
foreach (var keyword in KeyWords.Parse(originalUri)) {
// find suggestions matching that keyword
foreach (var suggestedUri in Uris.Where(u => u.Keywords.Contains(keyword)) {
// add a hit for keyword match
suggestionHits[suggestedUri] += 1;
}
}
// order by weight * hits
return suggestionHits.Keys
.OrderBy(s => s.Weight * suggestionHits[s])
.Select(s => s.Uri)
.ToArray();
}
}
class SuggestedUri {
public Uri Suggested { get; set; }
public int Weight { get; set; }
public Keyword[] Keywords;
}
class Keyword {
public string Value { get; set; }
public static Keyword[] Parse(Uri uri);
override Equals;
override GetHashCode;
}

Dictionary would be fine. Wether you store it as the interface type IDictionary or Dictionary itself wouldn't matter much in this case as it's not going to be passed much around, besides on the 404 page itself.
Have you considered doing some URL rewriting to still support the old URLs?

You can consider writing your own class logic and then assign that to a List data structure as following:
public class KeyValuesClass
{
private string a_key;
private string a_value;
public KeyValuesClass(string a_key, string a_value)
{
this.a_key = a_key;
this.a_value = a_value;
}
public string Key
{
get{ return a_key; }
set { a_key = value; }
}
public string Value
{
get{ return a_value; }
set { a_value = value; }
}
}
somewhere in the code
List<KeyValuesClass> my_key_value_list = new List<KeyValuesClass>();
my_key_value_list.Add(new KeyValuesClass("key", "value");
But you can consider Dictionary as our fellow programmer mentioned it above :)

Related

Unwanted unique constraint in many to many relationship

I'm trying to set up a Tagging tool for images. Basically I have two tables, one for pictures, and one for tags. Both are connected with a many to many setup. I can already add a single tag to a picture, and the same tag to different pictures. However, when I try to add a second tag to an image I get an exception complaining about a unique constraint that I simply don't see.
public class MediaEntity
{
public Guid Id { get; set; }
public string Name { get; set; }
public ICollection<TagEntity> Tags { get; set; }
}
public class TagEntity
{
public Guid Id { get; set; }
public string Name { get; set; }
public ICollection<MediaEntity> MediaEntities { get; set; }
}
public void updateMedia(MediaEntity model)
{
using (var db = new MediaContext(_dbLocation))
{
db.Update(model);
db.SaveChanges();
}
}
public class MediaContext : DbContext
{
private const string DB_NAME = "PT.db";
private string _path;
public DbSet<MediaEntity> MediaTable { get; set; }
public DbSet<TagEntity> TagTable { get; set; }
public MediaContext(string path)
{
_path = path;
ChangeTracker.AutoDetectChangesEnabled = false;
}
protected override void OnConfiguring(DbContextOptionsBuilder options)
=> options.UseSqlite($"Data Source={Path.Combine(_path, DB_NAME )}");
}
As far as I can tell my setup should create a normal many-to-many relationship, and it the database I also see pretty much this. EF automatically creates a TagTable, MediaTable, and MediaEntityTagEntityTable. But when I try to add a second tag I get this:
SqliteException: SQLite Error 19: 'UNIQUE constraint failed:
MediaEntityTagEntity.MediaEntitiesId, MediaEntityTagEntity.TagsId'.
Data from the table showing I can have the same tag on different pictures:
MediaEntitiesId
TagEntitiesId
1B48E85B-F097-4216-9B7A-0BA34E69CBFF
CF581257-F176-4CDF-BF34-09013DCEAA27
CE33F03F-5C80-492B-88C6-3C40B9BADC6C
CF581257-F176-4CDF-BF34-09013DCEAA27
523178A1-C7F8-4A69-9578-6A599C1BEBD5
0C45C9D1-7576-4C62-A495-F5EF268E9DF8
I don't see where this unique constaint comes in. How can I set up a proper many-to-many relationship?
I suspect the issue you may be running into is with the detached Media and associated Tags you are sending in. You are telling EF to apply an 'Update' to the media, but the DbContext will have no idea about the state of the Tags attached. Assuming some tags may have been newly attached, others are existing relationships. If the Context isn't tracking any of these Tags, it would treat them all as inserts, resulting in index violations (many to many) or duplicate data (many to one / one to many)
When dealing with associations like this, it is generally simpler to define more atomic actions like: AddTag(mediaId, tagId) and RemoveTag(mediaId, tagId)
If you are applying tag changes along with potential media field updates in a single operation I would recommend rather than passing entire entity graphs back and forth, to use a viewModel/DTO for the tag containing a collection of TagIds, from that apply your tag changes against the media server side after determining which tags have been added and removed.
I.e.:
public void updateMedia(MediaViewModel model)
{
using (var db = new MediaContext(_dbLocation))
{
var media = db.Medias.Include(x => x.Tags).Single(x => x.MediaId = model.MedialId);
// Ideally have a Timestamp/row version number to check...
if (media.RowVersion != model.RowVersion)
throw new StaleDataException("The media has been modified since the data was retrieved.");
// copy media fields across...
media.Name = model.Name;
// ... etc.
var existingTagIds = media.Tags
.Select(x => x.TagId)
.ToList();
var tagIdsToRemove = existingTagIds
.Except(model.TagIds)
.ToList();
var tagIdsToAdd = model.TagIds
.Except(existingTagIds)
.ToList();
if(tagIdsToRemove.Any())
media.Tags.RemoveRange(media.Tags.Where(x => tagIdsToRemove.Contains(x.TagId));
if(tagIdsToAdd.Any())
{
var tagsToAdd = db.Tags.Where(x => tagIdsToAdd.Contains(x.TagId)).ToList();
media.Tags.AddRange(tagsToAdd);
}
db.SaveChanges();
}
}
Using this approach the DbContext is never left guessing about the state of the media and associated tags. It helps guard against stale data overwrites and unintentional data tampering (if receiving data from web browsers or other unverifiable sources), and by using view models with the minimum required data, you improve performance by minimzing the amount of data sent over the wire and traps like lazy load hits by serializers.
I always explicitly create the join table. The Primary Key is the combination of the two 1:M FK attributes. I know EF is supposed to map automatically, but since it isn't, you can specify the structure you know you need.

Asp.net MVC change css on publish

We have an MVC application that is deployed as 3 different versions in production (seperate business areas demand seperate DBs and UIs). The only problem is that a few users use more than 1 of these applications and because they look vsually similar people get confused as to which one they are using.
I use web.config transforms to change the app title but what would like to do is deliver each one with a different css file. Is there a way to:
Use transforms on publish to edit an existing css file?
or
Swap the css file for another on publish?
Any help pointing me in the right direction would be great.
Thanks
What I did in a similar case : I dynamicly put a class on the body <body class="theme-site#AppSettingParam"> and i have only one CSS with override like :
.theme-site1 { background-color:blue; }
.theme-site2 { background-color:red; }
if a user uses multiple sites, it does not re-download the css and i have only one css to maintain.
This isn't the answer you're looking for right now, but if you do reconsider using the same site with different configurations, take a look at what I did recently to dynamically change CSS etc:
I decided that each 'version' of the website would use a unique reference in the query string. Based on this, I'll find the correct content, load the paths into a Model and send it to the view.
Here's the controller:
public ActionResult Index()
{
List<string> listOfAcceptableRef = new List<string>() { "uniqueCode1", "uniqueCode2" };
string uniqueRef=null;
if (Request.QueryString["ref"]!=null)
policyRef = Request.QueryString["ref"].ToLower();
if (string.IsNullOrWhiteSpace(uniqueRef) || (!string.IsNullOrWhiteSpace(uniqueRef) && !listOfAcceptableRef.Contains(uniqueRef)))
{
throw new Exception("This reference key is unknown.");
//return RedirectToAction("KeyError");
}
return View(GetPageContext(uniqueRef));
}
Grab the reference code from the query string and then generate a model containing the relevant CSS paths from a context factory.
Here's my model:
public class PageContext
{
public string Ref { get; set; }
public string TabId { get; set; }
public string TabName { get; set; }
public string SiteTitle { get; set; }
public string CssPath { get; set; }
public PageContext()
{
Products = new List<ProductInfo>();
}
}
And my context factory:
public class ContextFactory<T>
{
private ContextFactory()
{
}
static readonly Dictionary<string, Type> _dict = new Dictionary<string, Type>()
{
{ "uniqueRef1", Type.GetType("The.Full.Page.Namespace.UniqueSite1Context")},
{ "uniqueRef2", Type.GetType("The.Full.Page.Namespace.UniqueSite2Context")}
};
public static bool Create(string reference, out T context)
{
context = default(T);
Type type = null;
if (_dict.TryGetValue(reference, out type))
{
context = (T)Activator.CreateInstance(type);
return true;
}
return false;
}
}
And the actual context instance with the CSS paths etc:
public class UniqueSite1Context : PageContext
{
public UniqueSite1Context()
{
this.Ref = "uniqueSite1";
this.CssPath = "Content/UniqueSite1Context.css";
this.DisclaimerPath = "Content/UniqueSite1Context.pdf";
this.SiteTitle = "UniqueSite1";
}
}
After all that, just render the CSS using the model's paths:
#section Styles {
#{
string path = Url.Content("~") + Model.CssPath;
<link href="#path" rel="stylesheet" type="text/css" />
}
}
Architecturally speaking, you could extend this (or rather the concept of it) to use different logic and data contexts based on which 'site' the user goes to.
Have you considered transform files? They change the settings in your web.config file when you publish, based on the publish profile selected. Typically the profiles available by default is "Debug" and "Release", but you could add more like "Site1" and "Site2" with different CSS paths.
Take a look at how they work here. (I haven't used them myself so I can't help much in the way of code examples).

Update database items from the website

My current problem is (probably) not necessarily directly related to MVC 6, but how working with database actually works, and therefore any help/suggestions in this matter would be more than appreciated.
For the sake of this question, let's say that we have a very simple database with the following tables (C# classes) [we are using Entity Framework to work with the database]:
public class ShoppingUser
{
public int Id { get; set; }
public string UserName { get; set; }
public ICollection<ShoppingItem> Items { get; set; }
}
public class ShoppingItem
{
public int Id { get; set; }
public string Quantity { get; set; }
public string Text { get; set; }
public bool ToRemove { get; set; }//if item has been bought, it can be removed from the shopping list
}
This demo will be for a super duper simple shopping list app, where user (ShoppingUser who is registered in the system can have a List of ShoppingItem where user can decide on what is the text of the item (e.g. Bread, Butter, Tomatoes, ...) and also a quantity (3 pieces, 5kg, ... simple string)
Afterwards in my ASP.NET Core app, I have defined a repository which is communicating with the database and has access to the ShoppingItem class (as we are only interested in shopping items of currently logged in user).
Example of some method we could use here:
public IEnumerable<ShoppingItem> ReturnUserItems(string sUsername)
{
if (string.IsNullOrWhiteSpace(sUsername))
return null;
var result = _context.ShoppingUsers.Include(n => n.Items).Where(n => n.UserName == sUsername).FirstOrDefault();
if (result != null)
return result.Items;
else
return null;
}
Finally we have an API controller with JsonResult for either GET, POST, DELETE, ..., which is used for communication between client side AngularJs App and our server side logic.
Example of GET Method:
// GET: /<controller>/
[HttpGet("")]
public JsonResult Get(string sUserName)
{
try
{
var results = _repository.ReturnUserItems(User.Identity.Name);
if (results != null)
{
var result = Mapper.Map<IEnumerable<ShoppingItemViewModel>>(results);
return Json(result);
}
Response.StatusCode = (int)HttpStatusCode.OK;
}
catch (Exception ex)
{
Response.StatusCode = (int)HttpStatusCode.BadRequest;
return Json(new { Message = ex.Message });
}
return null;
}
Here comes the tricky part (at least for me). From video tutorials I have learned, that I should never (or almost never) expose my real database model to the website (I guess it's for security reasons). Due to that (as visible from my GET method above) I have declared my ShoppingItemViewModel which contains only properties I want to expose to the user (e.g. meaning that Id of my item is not visible).
This is how it looks like:
public class ShoppingItemViewModel
{
public string Quantity { get; set; }
[Required]
public string Text { get; set; }
[Required]
public bool ToRemove { get; set; }//if item has been bought, it can be removed from the shopping list
}
And for the communication from my AngularJS App I am using simple $http.get and $http.post calls for retrieving / posting updated data.
Finally the question:
My problem is, that if a user decides to either delete an item from his shopping list, or decides to change the content of either text / quantity (meaning that originally in the database it was tomatoes - 5 kg but he manages to buy only 2 kg and therefore changes the quantity to tomatoes - 3kg), how can the app understand which elements have actually been changed and how? The problem I have in this case is, that we are no longer exposing the database Id of the items.
If I was writing a desktop app, where I wouldn't have to create this sub view (ShoppingItemViewModel), my EntityFramework is intelligent enough to check & update all the changes in my database. Unfortunately in this case, I do not understand how this is achievable.
When I was thinking about it I came with the following: Add a new property into the ShoppingItem and ShoppingItemViewModel: public string sCustomKey {get; set; }, which would serve as a unique key for every item. This way, we no longer need to expose our database Id, but we are exposing the 'fake' one.
Second question:
I case my solution would be accurate, what is the best way to update items in the database? The only way I can think of is iterating through all the items in the database and manually check for changes?
Example of what I have in mind:
//IEnumerable<ShoppingItem> would be re-mapped result of ShoppingItemViewModel we have received back from the website
public void UpdateValues(IEnumerable<ShoppingItem> items, string sUserName)
{
//retrieves list of shopping items for specified customer
var allItems = _context.ShoppingUsers
.Include(n => n.Items)
.FirstOrDefault(n => n.UserName == sUserName);
//updates the values
foreach (var sItem in items)
{
var updatedItem = allItems.Items.FirstOrDefault(n => n.Text == sItem.sCustomKey);
if (updatedItem == null)
{
//create new item
var newItem = new ShoppingItem();
newItem.Text = sItem.Text;
newItem.ToRemove = sItem.ToRemove;
allItems.Items.Add(newItem);
}
else
updatedItem.ToRemove = sItem.ToRemove;
}
_context.SaveChanges();
}
But this approach does not seem right to me.
Any help regarding these matters would be more than appreciated as I am still learning how to work with ASP.NET Core and web projects.
In your first question, exposing the item ID in the ViewModels is fine. In your domain layer, you can add validation logic that those ID exists/valid item.
Alternatively, you can use a Guid for your item/product because the ID (int) can easily be predicted.
As far as updating the items, you should not use the "username" as Identifier (of the cart) because that can be predicted/altered by the calling client. You can use Guid either persisted(to Db) or
in-memory. You can add validation as well if this Guid belongs to this username/emailAddress. So updating the items in the cart, consider adding/removing one at a time if that is doable
instead of sending list of items.
I think you have misunderstood something.
Here comes the tricky part (at least for me). From video tutorials I have learned, that I should never (or almost never) expose my real database model to the website (I guess it's for security reasons). Due to that (as visible from my GET method above) I have declared my ShoppingItemViewModel which contains only properties I want to expose to the user (e.g. meaning that Id of my item is not visible).
ViewModel <=> Domain Model <=> ReadModel (Database Model)
The point is that you shouldn't use your ReadModel(Database model) as your ViewModel in Presentation Layer (MVC). All three models will have identity.

WCF DataContract with custom List Attribute

I have a WCF webservice, that exposes these classes:
[DataContract]
public class TemplatesFormat
{
List<DynAttribute> _dynsattributes = new List<DynAttribute>();
[DataMember]
public List<DynAttribute> DynsAttributes
{
get { return _dynsattributes; }
set { _dynsattributes = value; }
}
}
[DataContract]
public class DynAttribute
{
string _key = "";
string _val = "";
[DataMember]
public string Key
{
get { return _key; }
set { _key = value; }
}
[DataMember]
public string Value
{
get { return _val; }
set { _val = value; }
}
}
Basically, 2 classes. DynAttribute with 2 string attributes and TemplatesFormat, with an attribute that is a List of DynAttribute class.
So far, so good.
But, when I reference the web service from an ASP.NET web page and try to use the TemplatesFormat, I can't see the List attribute.
I mean, I actually "see" it, but it is not a list (does not contain an "Add()") and I don't know how to use it.
I think I am missing something related with de [DataContrat] and the fact that it is a custom type, since, I don't have the same problem with DynAttribute class (I see the Key and Value attributes because they are strings) but, I can't get it right for the List...
Any idea???
When you add reference to wcf service you need to change Collection Type to Generic List.
Please see my post wcf-proxy-returning-array-instead-of-list-even-though-collection-type-generic for more details and snipp picture.
WCF is meant to support consumption by many other platforms. Because List<DynAttribute> is not a primitive type, it is likely converting it to DynAttribute[].
In your consuming application. Try taking your variable and seeing if you can .ToList() it to turn it back into the List<DynAttribute> you're expecting.

ASP.NET - Avoid hardcoding paths

I'm looking for a best practice solution that aims to reduce the amount of URLs that are hard-coded in an ASP.NET application.
For example, when viewing a product details screen, performing an edit on these details, and then submitting the changes, the user is redirected back to the product listing screen. Instead of coding the following:
Response.Redirect("~/products/list.aspx?category=books");
I would like to have a solution in place that allows me to do something like this:
Pages.GotoProductList("books");
where Pages is a member of the common base class.
I'm just spit-balling here, and would love to hear any other way in which anyone has managed their application redirects.
EDIT
I ended up creating the following solution: I already had a common base class, to which I added a Pages enum (thanks Mark), with each item having a System.ComponentModel.DescriptionAttribute attribute containing the page's URL:
public enum Pages
{
[Description("~/secure/default.aspx")]
Landing,
[Description("~/secure/modelling/default.aspx")]
ModellingHome,
[Description("~/secure/reports/default.aspx")]
ReportsHome,
[Description("~/error.aspx")]
Error
}
Then I created a few overloaded methods to handle different scenarios. I used reflection to get the URL of the page through it's Description attribute, and I pass query-string parameters as an anonymous type (also using reflection to add each property as a query-string parameter):
private string GetEnumDescription(Enum value)
{
Type type = value.GetType();
string name = Enum.GetName(type, value);
if (name != null)
{
FieldInfo field = type.GetField(name);
if (field != null)
{
DescriptionAttribute attr = Attribute.GetCustomAttribute(field, typeof(DescriptionAttribute)) as DescriptionAttribute;
if (attr != null)
return attr.Description;
}
}
return null;
}
protected string GetPageUrl(Enums.Pages target, object variables)
{
var sb = new StringBuilder();
sb.Append(UrlHelper.ResolveUrl(Helper.GetEnumDescription(target)));
if (variables != null)
{
sb.Append("?");
var properties = (variables.GetType()).GetProperties();
foreach (var property in properties)
sb.Append(string.Format("{0}={1}&", property.Name, property.GetValue(variables, null)));
}
return sb.ToString();
}
protected void GotoPage(Enums.Pages target, object variables, bool useTransfer)
{
if(useTransfer)
HttpContext.Current.Server.Transfer(GetPageUrl(target, variables));
else
HttpContext.Current.Response.Redirect(GetPageUrl(target, variables));
}
A typical call would then look like so:
GotoPage(Enums.Pages.Landing, new {id = 12, category = "books"});
Comments?
I'd suggest that you derive your own class ("MyPageClass") from the Page class and include this method there:
public class MyPageClass : Page
{
private const string productListPagePath = "~/products/list.aspx?category=";
protected void GotoProductList(string category)
{
Response.Redirect(productListPagePath + category);
}
}
Then, in your codebehind, make sure that your page derives from this class:
public partial class Default : MyPageClass
{
...
}
within that, you can redirect just by using:
GotoProductList("Books");
Now, this is a bit limited as is since you'll undoubtedly have a variety of other pages like the ProductList page. You could give each one of them its own method in your page class but this is kind of grody and not smoothly extensible.
I solve a problem kind of like this by keeping a db table with a page name/file name mapping in it (I'm calling external, dynamically added HTML files, not ASPX files so my needs are a bit different but I think the principles apply). Your call would then use either a string or, better yet, an enum to redirect:
protected void GoToPage(PageTypeEnum pgType, string category)
{
//Get the enum-to-page mapping from a table or a dictionary object stored in the Application space on startup
Response.Redirect(GetPageString(pgType) + category); // *something* like this
}
From your page your call would be: GoToPage(enumProductList, "Books");
The nice thing is that the call is to a function defined in an ancestor class (no need to pass around or create manager objects) and the path is pretty obvious (intellisense will limit your ranges if you use an enum).
Good luck!
You have a wealth of options availible, and they all start with creating a mapping dictionary, whereas you can reference a keyword to a hard URL. Whether you chose to store it in a configuration file or database lookup table, your options are endless.
You have a huge number of options available here. Database table or XML file are probably the most commonly used examples.
// Please note i have not included any error handling code.
public class RoutingHelper
{
private NameValueCollecton routes;
private void LoadRoutes()
{
//Get your routes from db or config file
routes = /* what ever your source is*/
}
public void RedirectToSection(string section)
{
if(routes == null) LoadRoutes();
Response.Redirect(routes[section]);
}
}
This is just sample code, and it can be implemented any way you wish. The main question you need to think about is where you want to store the mappings. A simple xml file could do it:
`<mappings>
<map name="Books" value="/products.aspx/section=books"/>
...
</mappings>`
and then just load that into your routes collection.
public class BasePage : Page
{
public virtual string GetVirtualUrl()
{
throw new NotImplementedException();
}
public void PageRedirect<T>() where T : BasePage, new()
{
T page = new T();
Response.Redirect(page.GetVirtualUrl());
}
}
public partial class SomePage1 : BasePage
{
protected void Page_Load()
{
// Redirect to SomePage2.aspx
PageRedirect<SomePage2>();
}
}
public partial class SomePage2 : BasePage
{
public override string GetVirtualUrl()
{
return "~/Folder/SomePage2.aspx";
}
}

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