Lets say we have a 'Client' object:
(am just mentioning the attributes and the equals method alone of the 'Client' object below!!)
public class Client {
private Long clientId;
private String clientName;
private Integer status;
//getters and setters for above attributes
.....
...
//hashCode method
....
..
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Client other = (Client) obj;
if (clientId == null) {
if (other.clientId != null)
return false;
} else if (!clientId.equals(other.clientId))
return false;
if (clientName == null) {
if (other.clientName != null)
return false;
} else if (!clientName.equals(other.clientName))
return false;
if (status == null) {
if (other.status != null)
return false;
} else if (!status.equals(other.status))
return false;
return true;
}
}
From the above equals method itz clear that 'two' client objects are said to be equal if all the attributes of the two objects are identical.
Now assume a scenario where I need to compare two collections(named say incomingClients and existingClients) of Client objects.
The first collection(Collection incomingClients) was generated after reading the 'client' data from a csv/xls file.
The second collection(Collection existingClients) contains, all the existing clients currently in the system.
I can do the following code (using apache CollectionUtils)to get the 'common' clients.
Collection<Client> commonClients = (Collection<Client>)CollectionUtils.intersection(incomingClients,existingClients);
Now with the below code I can remove these commonClients from both the collections.
incomingClients.removeAll(commonClients);
existingClients.removeAll(commonClients);
The intention of removing the 'common clients objects' was that, we dont need to do 'any processing' for these records,
as we are really not at all interested in those records.
Now how can I figure out which are the entirely 'new clients' in the 'Collection incomingClients' collection?
(When I say 'new' it means a client having a new 'clientId' which doesnt exist in the 'Collection existingClients')
Also, how can I figure out which are the clients which needs 'modification'
(When I say 'modification' it means that the 'Collection incomingClients' and Collection existingClients'
have the same clientId, but, say, different 'clientName')
I know that we can do the normal 'for' loop('check below') to figure out the 'new'/'modification needed' clients.
But I thought of writing 'something new', whether we can achieve this using some classes/function in the 'Apache CollectionUtils' package.
Collection<Client> newClients = new ArrayList<Client>();
Collection<Client> toBeModifiedClients = new ArrayList<Client>();
boolean foundClient = false;
Client client = null;
for(Client incomingClient :incomingClients){
foundClient = false;
for(Client existingClient : existingClients){
if(existingClient.getClientId().equals(incomingClient.getClientId())){
client = existingClient;
foundClient = true;
break;
}
}
if(foundClient){
toBeModifiedClients.add(client);
}else{
//not found in existing. so this is completely new
newClients.add(incomingClient);
}
}
Am I 'complicating' a simple stuff??
Any thoughts??
First, yes, you are complicating "simple stuff". Your entire question could be summarized as follows:
Given collections A and B, how can I get the following using CollectionUtils:
A-B, using a particular function that determines equality
A∩B, using a particular function that determines equality
So, yes. CollectionUtils has what you need. Look at CollectionUtils.select().
Related
need small help about returning values based on arguments.
Setup of mocking contains expressions like
mockingObject
.Setup(_=>_.Select(It.IsAny<Expression<Func<Entity, bool>>>(),
It.IsAny<Func<IQueryable<Entity>, IOrderedQueryable<Entity>>>(),
It.IsAny<List<Expression<Func<Entity, object>>>>(), It.IsAny<int?>(), It.IsAny<int?>())))
.ReturnsAsync((Expression<Func<Entity,bool>>,Func<IQueryable<Entity>, IOrderedQueryable<Entity>>,List<Expression<Func<Entity,object>>>,int, int,EntityList());
But I'm getting error that Expression<Func<Entity,bool>> is a type which is not valid give context.
How should I manage Returns?
Need to mock:
public async Task<Result> UpdateNetworkStatus(string id, NetworkStatus status)
{
var network = _unitOfWork.NetworkRepository.SelectListAsync(x => x.Id == id).Result.FirstOrDefault();
if (network == null)
throw new Exception(nameof(network));
network.Status = status;
_unitOfWork.NetworkRepository.Update(network);
var saved = await _unitOfWork.Commit();
if (!saved)
return Result.Failure(new List<string>
{
"Failed to save"
});
return Result.Success();
}
Here I need to mock all possible scenarios.
Here is the example how I had manage to pass args to returns
unitOfWorkMock.Setup(_ => _.EntityRepository.SelectListAsync(It.IsAny<Expression<Func<Entity, bool>>>(),
It.IsAny<Func<IQueryable<Entity>, IOrderedQueryable<Entity>>>(),
It.IsAny<List<Expression<Func<Entity, object>>>>(), It.IsAny<int?>(), It.IsAny<int?>()))
.ReturnsAsync((Expression<Func<Entity, bool>> filter, Func<IQueryable<Entity>, IOrderedQueryable<Entity>> orderBy, List<Expression<Func<Entity, object>>> includes, int? page, int? pageSize) =>
{
if (filter == null)
return Entities();
return Entities().AsQueryable().Where(filter).ToList();
});
Currently I am querying a web service that returns a JSON string.
url = #"redacted url;
returnValue = new WebClient().DownloadString(url);
I am putting the return results into a list of items defined in a model class. I am then running a second JSON call searching a different field with that same search term.
url2 = #"redacted url2;
returnValue2 = new WebClient().DownloadString(url2);
I then create my lists and combine the lists using AddRange.
List<Order> shipments = JsonConvert.DeserializeObject<List<Order>>(returnValue);
List<Order> shipments2 = JsonConvert.DeserializeObject<List<Order>>(returnValue2);
shipments.AddRange(shipments2);
As a result there are some duplicates. To try and only return unique records I am using the command Distinct when sending to my MVC view from the controller.
return View(shipments.OrderBy(x => x.dtDateReceived).Distinct().ToList());
But for some reason it's still returning duplicates.
Any ideas on what I am doing wrong here?
Thanks in advance for any help!
I ended up correcting it using Shyju's comment above.
I changed the Distinct to the following.
return View(shipments.OrderBy(x => x.dtDateReceived).Distinct(new OrderComparer()).ToList());
Then built the following compare functions
// Custom comparer for the Order class
class OrderComparer : IEqualityComparer<Order>
{
// Orders are equal if their names and order numbers are equal.
public bool Equals(Order x, Order y)
{
//Check whether the compared objects reference the same data.
if (Object.ReferenceEquals(x, y)) return true;
//Check whether any of the compared objects is null.
if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null))
return false;
//Check whether the order's properties are equal.
return x.sWorkOrderNumber == y.sWorkOrderNumber && x.sCustomerOrderName == y.sCustomerOrderName;
}
// If Equals() returns true for a pair of objects
// then GetHashCode() must return the same value for these objects.
public int GetHashCode(Order order)
{
//Check whether the object is null
if (Object.ReferenceEquals(order, null)) return 0;
//Get hash code for the sCustomerOrderName field if it is not null.
int hashOrderName = order.sCustomerOrderName == null ? 0 : order.sCustomerOrderName.GetHashCode();
//Get hash code for the sWorkOrderNumber field.
int hashOrderCode = order.sWorkOrderNumber.GetHashCode();
//Calculate the hash code for the order.
return hashOrderName ^ hashOrderCode;
}
}
I 've built an ASP.NET website using EF. I created a DataContext class which implements the singleton pattern. My DAO classes (singletons too) instanciate this datacontext and store it in a property. They use it in order to query the SQLServer DataBase. This worked ok for 3 months but I suddenly got exception messages like :"Connection must be valid and open / connection already open". It seemed that datacontext was not disposed. The only change, according to me, was the data size and number of users increasing.
I then found multiple posts saying that singleton was a bad idea foe datacontext, so I tried to instanciate datacontext in a using statement in every request and that resolved the problem, except for update queries which had no effects in database. I had to attach the db object to the context and then set its EntityState to "modified" to have my SaveChanges work.
Like this :
public bool DoucheXpsu(as_headers session) {
using (MyDBEntities MyContext = new MyDBEntities()) {
try {
as_status status = GetStatus(session);
if (status != null) {
if (status.mainstatusvalue == 300) {
status.DateDoucheXpsu = DateTime.Now;
status.DoucheXpsu = 1;
MyContext.as_status.Attach(status);
MyContext.ObjectStateManager.ChangeObjectState(status, EntityState.Modified);
MyContext.SaveChanges();
return true;
} else {
return false;
}
} else {
return false;
}
} catch (OptimisticConcurrencyException) {
return false;
} catch (Exception) {
return false;
}
}
}
The problem is that it actually didn't work for ONE method (which has nothing different from the other update method) !
The exception occured as I tried to attach the object : "The object cannot be attached because it is already in the object context. An object can only be reattached when it is in an unchanged state. " So I had to comment the attach and ChangeObjectState methods to have it work as expected :
public bool SetSessionToDelete(string numSession) {
using (MyDBEntities MyContext = new MyDBEntities()) {
try {
view_headerStatus view = (from v in MyContext.view_headerStatus
where v.CodeSession == numSession
where v.lastinserted == 1
select v).First();
if (view != null) {
as_status status = (from s in MyContext.as_status
where s.jobclsid == view.jobclsid
where s.lastinserted == 1
select s).First();
if (status != null) {
status.DeleteSession = 1;
//MyContext.as_status.Attach(status);
//MyContext.ObjectStateManager.ChangeObjectState(status, EntityState.Modified);
MyContext.SaveChanges();
return true;
} else {
return false;
}
} else {
return false;
}
} catch (OptimisticConcurrencyException) {
return false;
} catch (Exception) {
return false;
}
}
}
The question is WHY should this one behave differently ???
I've read many posts about EF and dataContext but I feel I'm missing something. I would be glad if anyone can help.
Thanks.
In your first example, this line here:
as_status status = GetStatus(session);
I would assume this populates using a DIFFERENT context, and when it leaves the GetStatus() method the context it used to load is disposed. That is why your subsequent Attach() works. However in your second example you do not need to attach because it was loaded using the current (connected) context.
To solve you may want to either pass the context to your methods like GetStatus() resulting in no need to reattach. I don't typically reattach unless I am resurrecting an object over the wire or from a file.
I've got data returned from my JavaScript client that just includes the data that has changed. That is, I may have an array with each row containing 10 columns of JSON downloaded, but on the Update, only the data that is returned to me is the data that got updated. On my update, I only want to update those columns that are changed (not all of them).
In other words, I have code like below but because I'm passing in an instance of the "President" class, I have no way of knowing what actually came in on the original JSON.
How can I just update what comes into my MVC3 update method and not all columns. That is, 8 of the columns may not come in and will be null in the "data" parameter passed in. I don't want to wipe out all my data because of that.
[HttpPost]
public JsonResult Update(President data)
{
bool success = false;
string message = "no record found";
if (data != null && data.Id > 0)
{
using (var db = new USPresidentsDb())
{
var rec = db.Presidents.FirstOrDefault(a => a.Id == data.Id);
rec.FirstName = data.FirstName;
db.SaveChanges();
success = true;
message = "Update method called successfully";
}
}
return Json(new
{
data,
success,
message
});
}
rec.FirstName = data.FirstName ?? rec.FirstName;
I would use reflection in this case because the code will be too messy like
if (data.FirstName != null)
rec.FirstName = data.FirstName
.
.
.
and so on for all the fields
Using reflection, it would be easier to do this. See this method
public static void CopyOnlyModifiedData<T>(T source, ref T destination)
{
foreach (var propertyInfo in source.GetType().GetProperties())
{
object value = propertyInfo.GetValue(source, null);
if (value!= null && !value.GetType().IsValueType)
{
destination.GetType().GetProperty(propertyInfo.Name, value.GetType()).SetValue(destination, value, null);
}
}
}
USAGE
CopyOnlyModifiedData<President>(data, ref rec);
Please mind that, this won't work for value type properties.
I am working on an ASP.Net MVC app and I want to show a confirmation page after the user edits some data. What I would like to show is a list of the pending changes that the user made to the model.
For example,
Are you sure you want to make the following changes:
FieldName:
Previous Value: XXX
New Value: YYY
I know I can read my stored value from the database and compare it with the POSTed object but I want this to work generally. What would be some good ways to approach this?
To clarify, I am looking for a general way to get a "diff" of the pending changes. I already know how to get the previous and pending changes. Kind of like how TryUpdateModel() can attempt to update any Model with posted values. I'd like a magical GetPendingModelChanges() method that can return a list of something like new PendingChange { Original = "XXX", NewValue = "YYY"} objects.
You might be doing this already but I wouldn't send my model to the view, create a viewmodel. In this case I would map the model data to the viewmodel twice, my viewmodel might contain OrderInput and OrderInputOrig. Then stick OrderInputOrig in hidden fields. On post back you can compare the values and then redirect, if something changed, to a display view with the original and the changes for confirmation.
Maybe something like this:
[HttpPost]
public ActionResult Edit(CustomerInput cutomerInput)
{
var changes = PublicInstancePropertiesEqual(cutomerInput.OriginalCustomer, cutomerInput.Customer);
if (changes != null)
{
cutomerInput.WhatChangeds = changes;
return View("ConfirmChanges", cutomerInput);
}
return View();
}
public ActionResult ConfirmChanges(CustomerInput customerInput)
{
return View(customerInput);
}
from: Comparing object properties in c#
public static Dictionary<string, WhatChanged> PublicInstancePropertiesEqual<T>(T self, T to, params string[] ignore) where T : class
{
Dictionary<string, WhatChanged> changes = null;
if (self != null && to != null)
{
var type = typeof(T);
var ignoreList = new List<string>(ignore);
foreach (System.Reflection.PropertyInfo pi in type.GetProperties(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance))
{
if (!ignoreList.Contains(pi.Name))
{
var selfValue = type.GetProperty(pi.Name).GetValue(self, null);
var toValue = type.GetProperty(pi.Name).GetValue(to, null);
if (selfValue != toValue && (selfValue == null || !selfValue.Equals(toValue)))
{
if (changes == null)
changes = new Dictionary<string, WhatChanged>();
changes.Add(pi.Name, new WhatChanged
{
OldValue = selfValue,
NewValue=toValue
});
}
}
}
return changes;
}
return null;
}
Coming in very late here, but I created a library to do this on MVC models and providing "readable" diffs for humans using MVC ModelMetadata:
https://github.com/paultyng/ObjectDiff
It gives me output when I save a Model similar to:
Status: 'Live', was 'Inactive'
Phone: '123-456-7898', was '555-555-5555'
Etc.
use the TempData Dictionary.
TempData["previousValue"];
TempData["newValue"];