Imagine you've got n pages, each of which approximately shares the same sort of model but that model has to be in a particular state before you can access certain pages.
So if the user types in a URL to take them to page m, but this page is not accessible at the moment, the controller adds an error message to a collection of errors in TempData then redirects to page m-1.
The problem is when page m-1 is also not accessible. If we add a message to the same collection (with the same key) in TempData, we don't see it on page m-2 as it gets removed from TempData before the request for page m-2 gets underway.
I can imagine a solution where we have multiple error keys and each time we want to add an error or get errors back we try each key in turn, but has anyone got any better ideas? (I know that in theory I could work out the correct page to redirect to straight off but that is going to take a lot of rework and I don't have much time!)
EDIT:
This is the sort of thing I was thinking about:
protected void AddError(string error)
{
int keyCounter;
var errors = GetErrors(out keyCounter);
errors.Add(error);
TempData.Remove(GetKey(keyCounter + 1));
TempData[GetKey(keyCounter + 1)] = errors;
}
protected List<string> GetErrors()
{
int jnk;
return GetErrors(out jnk);
}
private string GetKey(int i)
{
return string.Format("ErrorKey:{0}", i);
}
private List<string> GetErrors(out int keyCounter)
{
keyCounter = 0;
List<string> errors = null;
for (int ii = 0; ii < MaxErrorKeyCounter; ii++)
{
string tryKey = GetKey(ii);
if (TempData.ContainsKey(tryKey))
{
keyCounter = ii;
errors = (List<string>)TempData[tryKey];
}
}
if (errors == null)
errors = new List<string>();
return errors;
}
Why not just use the Session?
Related
The project I am working is 'University Management System' and it's a big one. Right now, I am implementing the student registration section that works fine (A small portion of the project). I've used 'Three-Tier Architecture' and 'ORM - EF' in ASP.NET MVC template. In the project, I need to do some validations for registering students depending upon their year, department etc. So there are sections like DAL, BLL, finally controller and view. I've done the validations in the controller and getting the data from BLL that again retrieves data from DAL (This is the simple condition of 'Three-Tier Architecture'). So my questions are:
1) Is it OK to do the validations in the controller?
2) If not and need to do it in the BLL, will it be just fine and why or I can
continue doing it in the controller?
Note: To me, doing the validations in the controller or BLL seems OK and the same. Does it have any effect?
Right now, I've done the following:
DAL:
public List<Student> Add(int studentID, string studentName, string email, DateTime regDate)
{
List<Student> lst = null;
Student aStudent = new Student();
aStudent.StudentID = studentID;
aStudent.StudentName = studentName;
aStudent.Email = email;
aStudent.RegDate = regDate;
try
{
db.Students.Add(aStudent);
db.SaveChanges();
}
catch (Exception ex)
{
ex.ToString();
}
return lst;
}
BLL:
public List<Student> Add(int studentID, string studentName, string email, DateTime regDate)
{
return aStudentGateway.Add(studentID, studentName, email, regDate);
}
Controller:
/**Student Registration - Starts**/
[HttpPost]
public ActionResult AddStudent(Student aStudent)
{
List<Department> departments = aDepartmentManager.GetAllDepartments();
List<DepartmentViewModel> departmentsViewModel = aDepartmentManager.GetAllDepartmentViewModel();
DateTime yearInDateTime = Convert.ToDateTime(Request.Form["RegDate"]);
string extractYear = yearInDateTime.ToString();
var year = DateTime.Parse(extractYear).Year;
int department = Convert.ToInt32(Request.Form["Department"]);
List<Student> studentList = aStudentManager.GetAllStudents();
int count = 1;
var query = (from c in studentList
where c.Department == department && c.Year == year
select c).ToList();
foreach (var c in query)
{
if (query.Count() > 0)
{
int m = Convert.ToInt32(c.StudentID);
count = m + 1; //Incrementing the numbers by one with the table column
}
else
{
int m = 1;
count = m + 1; //Incrementing the numbers by one with the variable assigned one
}
}
Student student = new Student();
student.StudentName = Request.Form["StudentName"];
student.Email = Request.Form["Email"];
student.RegDate = Convert.ToDateTime(Request.Form["RegDate"]);
student.StudentID = count;
if (aStudentManager.ExistEmailAny(student.Email))
{
ViewBag.ErrorMessage = "Email already exists";
}
else
{
aStudentManager.Add(aStudent.StudentID, aStudent.StudentName, aStudent.Email, aStudent.RegDate);
ViewBag.Message = "Registration successful. See below to verify.";
/**This section used to show student details after registration**/
var result = (from c in departments
join d in departmentsViewModel on c.DepartmentID equals d.DepartmentId
where d.DepartmentId == department
select c);
foreach (var items in result)
{
if (count.ToString().Length > 1)
{
ViewBag.StudentID = items.Code + "-" + year + "-" + "0" + count;
}
else
{
ViewBag.StudentID = items.Code + "-" + year + "-" + "00" + count;
}
StudentViewModel.StudentID = student.StudentID;
StudentViewModel.StudentName = student.StudentName;
StudentViewModel.Email = student.Email;
StudentViewModel.RegDate = student.RegDate;
}
/**This section used to show student details after registration**/
}
return View();
}
/**Student Registration - Ends**/
I would provide multiple steps of validation in the different layers, depending on the context and the meaning of the layer.
First, it's a best practice to provide validation both on client and server side.
For the client side you should provide field checks for required fields and other simple validations. If you are using MVC you can use data annotations.
The same validation should be replicated in the controller. Here you should fail fast applying some kind of contract to the parameters that have been passed. One good practice is using Code Contracts that provide preconditions that need to be satisfied to go on in your pipeline of execution.
In the business layer provide the check that needs to be done in the business logic.
Finally in the data access layer provide all the checks that are needed to persist your data. If you are using EF a good practice is implementing the IValidatableObject for your entity classes. Here in Scott Gu's blog you can find a post that explains this technique.
Even though this approach look like it will introduce repetitions, it will provide consistency in your data and separate concerns between your layers.
1) Is it OK to do the validations in the controller?
No at all, it would be more better to use Data Annotation Validator Attributes, and to do validation in your model class.
Second thing, you're doing some stuff of DAL in your controller, like
List<Department> departments = aDepartmentManager.GetAllDepartments();
List<DepartmentViewModel> departmentsViewModel = aDepartmentManager.GetAllDepartmentViewModel();
var query = (from c in studentList
where c.Department == department && c.Year == year
select c).ToList();
These all queries should be in DAL, which is exact use of DAL to interact with the database, and keep your controller clean.
Third thing,
If you pass Student to the controller, then not need to get each attribute using Request.Form.
Hope this make sense!
I am using a WCF Data Services class that exposes an entity framework model via the OData protocol like so:
public class Service : EntityFrameworkDataService<MyEntities>
{
public static void InitializeService(DataServiceConfiguration config)
{
config.UseVerboseErrors = true;
config.SetEntitySetAccessRule("*", EntitySetRights.All);
config.SetServiceOperationAccessRule("*", ServiceOperationRights.All);
config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V3;
}
}
I consume this service through a service reference in a web solution. I am having problems including all the navigation properties for the entity. I cannot use the following syntax because I do not know what type of entity the user may be requesting:
I CANNOT USE
MyEntities.Customer.Expand("Address");
or
MyEntities.Customer.Include("Address");
What I am currently doing is building a URI string with the $expand=Entity1,Entity2 syntax and then executing that against my service as follows:
public static QueryOperationResponse<object> GetList(string entitySetName, params string[] preloads)
{
StringBuilder stringBuilder = new StringBuilder();
string queryString = string.Empty;
object result = null;
Uri dataAccessURI;
stringBuilder.Append(ServiceReferenceURI.AbsoluteUri);
stringBuilder.Append(entitySetName);
if (preloads != null)
{
for (int i = 0; i <= preloads.Length - 1; i++)
{
queryString = i == 0 ? "?$expand=" : ",";
stringBuilder.AppendFormat("{0}{1}", queryString, preloads[i]);
}
}
dataAccessURI = new Uri(stringBuilder.ToString());
try
{
result = TitanEntities.Execute<object>(dataAccessURI, "GET", true);
}
catch (Exception ex)
{
// log any errors to the console
WriteConsoleMessage(ex.Message, DataAccessEventType.Error);
}
return (QueryOperationResponse<object>)result;
resulting URI string is similar to this:
http://192.168.0.196/Service.svc/AliquotPreparation?$expand=Aliquot,AliquotPrepBatch,AnalysisPreparationMethod,Unit,Employee,Unit,PreparationMethod,State
To me this is a crappy implementation. It is all I could come up with right now though. The problem is, if there are A LOT of navigation properties the $expand command gets too long and the URI reaches it's character limit!
So how can I implement this through a service reference? I would greatly appreciate someone's help!!!
I am getting rss feed from a another website and in case that website shut down, I don't want to get an error. So in order to avoid from error I am trying to save rss feeds to database and if the rss server shuts down I will be able to get feed from my database.
I also want to keep only 6 feed in database. If new feed comes I want to delete the last feed by PublishDate
public static List<Rss.News> GetRssFeed(ApplicationDbContext db)
{
try
{
XDocument feedXml = XDocument.Load("http://www.gib.gov.tr/
rss/haberguncel.php");
var feeds = from feed in feedXml.Descendants("item")
select new Rss.News
{
Title = feed.Element("title").Value,
Link = feed.Element("link").Value,
Description = feed.Element("description").Value,
PublishDate=feed.Element("pubdate").Value
};
int counter = 0;
var itemE = db.News.FirstOrDefault();
if (itemE != feeds.First())
{
foreach (var itemC in feeds)
{
if (!db.News.Contains(itemC))
{
db.News.Add(itemC);
db.SaveChanges();
counter += 1;
}
else
{
break;
}
if (counter == 6) { break; }
}
}
return feeds.ToList();
}
catch (Exception)
{
// i will get data from database here.
}
}
I am getting this error when I run this code:
Unable to create a constant value of type
'...Models.Rss+News'. Only primitive types or enumeration
types are supported in this context.
The error is resulting from this line:
if (!db.News.Contains(itemC))
In order to do this type of evaluation at the database level, Entity Framework must be able to convert item being compared (itemC) into a constant value, which it cannot do with this type, hence your error. You can try casting db.News to a list, first, which would switch the evaluation over to in-memory instead at the the database, i.e.:
var news = db.News.ToList();
if (news.Contains(itemC))
However, you'll have to evaluate how that might affect your application's performance. Alternatively, you simply query on a particular value that you determine as the "key" for lookup. For example, you might say that Link will only ever match if it's the same item, so based on that:
if (!db.News.Any(m => m.Link == itemC.Link))
I have a system whereby users can upload sometimes large(100-200 MB) files from within an MVC3 application. I would like to not block the UI while the file is uploading, and after some research, it looked like the new AsyncController might let me do what I'm trying to do. Problem is - every example I have seen isn't really doing the same thing, so I seem to be missing one crucial piece. After much futzing and fiddling, here's my current code:
public void CreateAsync(int CompanyId, FormCollection fc)
{
UserProfile up = new UserRepository().GetUserProfile(User.Identity.Name);
int companyId = CompanyId;
// make sure we got a file..
if (Request.Files.Count < 1)
{
RedirectToAction("Create");
}
HttpPostedFileBase hpf = Request.Files[0] as HttpPostedFileBase;
if (hpf.ContentLength > 0)
{
AsyncManager.OutstandingOperations.Increment();
BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += (o, e) =>
{
string fileName = hpf.FileName;
AsyncManager.Parameters["recipientId"] = up.id;
AsyncManager.Parameters["fileName"] = fileName;
};
worker.RunWorkerCompleted += (o, e) => { AsyncManager.OutstandingOperations.Decrement(); };
worker.RunWorkerAsync();
}
RedirectToAction("Uploading");
}
public void CreateCompleted(int recipientId, string fileName)
{
SystemMessage msg = new SystemMessage();
msg.IsRead = false;
msg.Message = "Your file " + fileName + " has finished uploading.";
msg.MessageTypeId = 1;
msg.RecipientId = recipientId;
msg.SendDate = DateTime.Now;
SystemMessageRepository.AddMessage(msg);
}
public ActionResult Uploading()
{
return View();
}
Now the idea here is to have the user submit the file, call the background process which will do a bunch of things (for testing purposes is just pulling the filename for now), while directing them to the Uploading view which simply says "your file is uploading...carry on and we'll notify you when it's ready". The CreateCompleted method is handling that notification by inserting a message into the users's message queue.
So the problem is, I never get the Uploading view. Instead I get a blank Create view. I can't figure out why. Is it because the CreateCompleted method is getting called which shows the Create view? Why would it do that if it's returning void? I just want it to execute silently in the background, insert a message and stop.
So is this the right approach to take at ALL? my whole reason for doing it is with some network speeds, it can take 30 minutes to upload a file and in its current version, it blocks the entire application until it's complete. I'd rather not use something like a popup window if I can avoid it, since that gets into a bunch of support issues with popup-blocking scripts, etc.
Anyway - I am out of ideas. Suggestions? Help? Alternate methods I might consider?
Thanks in advance.
You are doing it all wrong here. Assume that your action name is Create.
CreateAsync will catch the request and should be a void method and returns nothing. If you have attributes, you should apply them to this method.
CreateCompleted is your method which you should treat as a standard controller action method and you should return your ActionResult inside this method.
Here is a simple example for you:
[HttpPost]
public void CreateAsync(int id) {
AsyncManager.OutstandingOperations.Increment();
var task = Task<double>.Factory.StartNew(() => {
double foo = 0;
for(var i = 0;i < 1000; i++) {
foo += Math.Sqrt(i);
}
return foo;
}).ContinueWith(t => {
if (!t.IsFaulted) {
AsyncManager.Parameters["headers1"] = t.Result;
}
else if (t.IsFaulted && t.Exception != null) {
AsyncManager.Parameters["error"] = t.Exception;
}
AsyncManager.OutstandingOperations.Decrement();
});
}
public ActionResult CreateCompleted(double headers1, Exception error) {
if(error != null)
throw error;
//Do what you need to do here
return RedirectToAction("Index");
}
Also keep in mind that this method will still block the till the operation is completed. This is not a "fire and forget" type async operation.
For more info, have a look:
Using an Asynchronous Controller in ASP.NET MVC
Edit
What you want here is something like the below code. Forget about all the AsyncController stuff and this is your create action post method:
[HttpPost]
public ActionResult About() {
Task.Factory.StartNew(() => {
System.Threading.Thread.Sleep(10000);
if (!System.IO.Directory.Exists(Server.MapPath("~/FooBar")))
System.IO.Directory.CreateDirectory(Server.MapPath("~/FooBar"));
System.IO.File.Create(Server.MapPath("~/FooBar/foo.txt"));
});
return RedirectToAction("Index");
}
Notice that I waited 10 seconds there in order to make it real. After you make the post, you will see the it will return immediately without waiting. Then, open up the root folder of you app and watch. You will notice that a folder and file will be created after 10 seconds.
But (a big one), here, there is no exception handling, a logic how to notify user, etc.
If I were you, I would look at a different approach here or make the user suffer and wait.
I'm looking at using ELMAH for the first time but have a requirement that needs to be met that I'm not sure how to go about achieving...
Basically, I am going to configure ELMAH to work under asp.net MVC and get it to log errors to the database when they occur. On top of this I be using customErrors to direct the user to a friendly message page when an error occurs. Fairly standard stuff...
The requirement is that on this custom error page I have a form which enables to user to provide extra information if they wish. Now the problem arises due to the fact that at this point the error is already logged and I need to associate the loged error with the users feedback.
Normally, if I was using my own custom implementation, after I log the error I would pass through the ID of the error to the custom error page so that an association can be made. But because of the way that ELMAH works, I don't think the same is quite possible.
Hence I was wondering how people thought that one might go about doing this....
Cheers
UPDATE:
My solution to the problem is as follows:
public class UserCurrentConextUsingWebContext : IUserCurrentConext
{
private const string _StoredExceptionName = "System.StoredException.";
private const string _StoredExceptionIdName = "System.StoredExceptionId.";
public virtual string UniqueAddress
{
get { return HttpContext.Current.Request.UserHostAddress; }
}
public Exception StoredException
{
get { return HttpContext.Current.Application[_StoredExceptionName + this.UniqueAddress] as Exception; }
set { HttpContext.Current.Application[_StoredExceptionName + this.UniqueAddress] = value; }
}
public string StoredExceptionId
{
get { return HttpContext.Current.Application[_StoredExceptionIdName + this.UniqueAddress] as string; }
set { HttpContext.Current.Application[_StoredExceptionIdName + this.UniqueAddress] = value; }
}
}
Then when the error occurs, I have something like this in my Global.asax:
public void ErrorLog_Logged(object sender, ErrorLoggedEventArgs args)
{
var item = new UserCurrentConextUsingWebContext();
item.StoredException = args.Entry.Error.Exception;
item.StoredExceptionId = args.Entry.Id;
}
Then where ever you are later you can pull out the details by
var item = new UserCurrentConextUsingWebContext();
var error = item.StoredException;
var errorId = item.StoredExceptionId;
item.StoredException = null;
item.StoredExceptionId = null;
Note this isn't 100% perfect as its possible for the same IP to have multiple requests to have errors at the same time. But the likely hood of that happening is remote. And this solution is independent of the session, which in our case is important, also some errors can cause sessions to be terminated, etc. Hence why this approach has worked nicely for us.
The ErrorLogModule in ELMAH (version 1.1 as of this writing) provides a Logged event that you can handle in Global.asax and which you can use to communicate details, say via HttpContext.Items collection, to your custom error page. If you registered the ErrorLogModule under the name ErrorLog in web.config then your event handler in Global.asax will look like this:
void ErrorLog_Logged(object sender, ErrorLoggedEventArgs args)
{
var id = args.Entry.Id
// ...
}