I am developing a wcf service for Windows 8 APP. But I'm choked up at one point.
The following method, it is coming data in the database using entity. But this the data returns back to a class type. My question , if result is null what can I sent person who will this method
public AnketorDTO AnketorBul(string tc, string pass)
{
_entity = new AnketDBEntities();
var result = (from i in _entity.Anketors
where i.TC == tc
where i.Sifre == pass
select i).ToList();
if (!result.Any())
-->>> return new AnketorDTO();
Anketor anketor = result.First();
return Converter.ConvertAnketorToAnketorDTO(anketor);
}
with this methot I SENT it by creating a new class type but part which use this methot does not work because the values become null. how can we prevent it.
Client :
AnketorDTO anketor = await client.AnketorBulAsync(txtKullanici.Text, txtSifre.Password);
**if (anketor != null)
lblError.Text = anketor.Adi;**
else
lblError.Text = "Hata";
Can you try this method to see, if it works?
_entity = new AnketDBEntities();
var result = _entity.Anketors.FirstOrDefault(yourexpressions);
Related
_context.Update(v) ;
_context.SaveChanges();
When I use this code then SQL Server adds a new record instead of updating the
current context
[HttpPost]
public IActionResult PageVote(List<string> Sar)
{
string name_voter = ViewBag.getValue = TempData["Namevalue"];
int count = 0;
foreach (var item in Sar)
{
count = count + 1;
}
if (count == 6)
{
Vote v = new Vote()
{
VoteSarparast1 = Sar[0],
VoteSarparast2 = Sar[1],
VoteSarparast3 = Sar[2],
VoteSarparast4 = Sar[3],
VoteSarparast5 = Sar[4],
VoteSarparast6 = Sar[5],
};
var voter = _context.Votes.FirstOrDefault(u => u.Voter == name_voter && u.IsVoted == true);
if (voter == null)
{
v.IsVoted = true;
v.Voter = name_voter;
_context.Add(v);
_context.SaveChanges();
ViewBag.Greeting = "رای شما با موفقیت ثبت شد";
return RedirectToAction(nameof(end));
}
v.IsVoted = true;
v.Voter = name_voter;
_context.Update(v);
_context.SaveChanges();
return RedirectToAction(nameof(end));
}
else
{
return View(_context.Applicants.ToList());
}
}
You need to tell the DbContext about your entity. If you do var vote = new Vote() vote has no Id. The DbContext see this and thinks you want to Add a new entity, so it simply does that. The DbContext tracks all the entities that you load from it, but since this is just a new instance, it has no idea about it.
To actually perform an update, you have two options:
1 - Load the Vote from the database in some way; If you get an Id, use that to find it.
// Loads the current vote by its id (or whatever other field..)
var existingVote = context.Votes.Single(p => p.Id == id_from_param);
// Perform the changes you want..
existingVote.SomeField = "NewValue";
// Then call save normally.
context.SaveChanges();
2 - Or if you don't want to load it from Db, you have to manually tell the DbContext what to do:
// create a new "vote"...
var vote = new Vote
{
// Since it's an update, you must have the Id somehow.. so you must set it manually
Id = id_from_param,
// do the changes you want. Be careful, because this can cause data loss!
SomeField = "NewValue"
};
// This is you telling the DbContext: Hey, I control this entity.
// I know it exists in the DB and it's modified
context.Entry(vote).State = EntityState.Modified;
// Then call save normally.
context.SaveChanges();
Either of those two approaches should fix your issue, but I suggest you read a little bit more about how Entity Framework works. This is crucial for the success (and performance) of your apps. Especially option 2 above can cause many many issues. There's a reason why the DbContext keep track of entities, so you don't have to. It's very complicated and things can go south fast.
Some links for you:
ChangeTracker in Entity Framework Core
Working with Disconnected Entity Graph in Entity Framework Core
I am trying to perform a SELECT on the M1lhao table of Sorteio entity (database).
I don't want to go the traditional "string query" or AddWithParameter() way, i wanted to use the MVC4 EF5 available methods.
The following code passes the entire Table to the View, that i can do a foreach in the View and all works fine. What i am looking for is how can i do a SQL query, so i can pass only the element(s) i want, sorted DESCending (for example), obviously on a List and obeying the Model that the View expects.
Essentially i want a replacement for (i tried variants too, db.Milhao, etc):
var data = db.Database.ExecuteSqlCommand("SELECT * From M1lhao WHERE DrawID = {0}", id);
The problem with Find() is that it only searches primary keys.
The complete code:
public class M1lhaoController : Controller
{
private Sorteio db = new Sorteio();
public ActionResult Index(int id = 1)
{
var data = db.Database.ExecuteSqlCommand("SELECT * From M1lhao WHERE DrawID = {0}", id); // the variable data comes as -1
M1lhao m1lhao = db.M1lhao.Find(id);
if (m1lhao == null)
{
return HttpNotFound();
}
return View(db.M1lhao.ToList());
}
}
Thank you.
You can try as shown below.
var data = db.M1lhao.Where(m=>m.DrawID == id).Select(p=>p);
You can learn more about Method-Based Query Syntax : Projection
So I have a standard service reference proxy calss for MS CRM 2013 (i.e. right-click add reference etc...) I then found the limitation that CRM data calls limit to 50 results and I wanted to get the full list of results. I found two methods, one looks more correct, but doesn't seem to work. I was wondering why it didn't and/or if there was something I'm doing incorrectly.
Basic setup and process
crmService = new CrmServiceReference.MyContext(new Uri(crmWebServicesUrl));
crmService.Credentials = System.Net.CredentialCache.DefaultCredentials;
var accountAnnotations = crmService.AccountSet.Where(a => a.AccountNumber = accountNumber).Select(a => a.Account_Annotation).FirstOrDefault();
Using Continuation (something I want to work, but looks like it doesn't)
while (accountAnnotations.Continuation != null)
{
accountAnnotations.Load(crmService.Execute<Annotation>(accountAnnotations.Continuation.NextLinkUri));
}
using that method .Continuation is always null and accountAnnotations.Count is always 50 (but there are more than 50 records)
After struggling with .Continutation for a while I've come up with the following alternative method (but it seems "not good")
var accountAnnotationData = accountAnnotations.ToList();
var accountAnnotationFinal = accountAnnotations.ToList();
var index = 1;
while (accountAnnotationData.Count == 50)
{
accountAnnotationData = (from a in crmService.AnnotationSet
where a.ObjectId.Id == accountAnnotationData.First().ObjectId.Id
select a).Skip(50 * index).ToList();
accountAnnotationFinal = accountAnnotationFinal.Union(accountAnnotationData).ToList();
index++;
}
So the second method seems to work, but for any number of reasons it doesn't seem like the best. Is there a reason .Continuation is always null? Is there some setup step I'm missing or some nice way to do this?
The way to get the records from CRM is to use paging here is an example with a query expression but you can also use fetchXML if you want
// Query using the paging cookie.
// Define the paging attributes.
// The number of records per page to retrieve.
int fetchCount = 3;
// Initialize the page number.
int pageNumber = 1;
// Initialize the number of records.
int recordCount = 0;
// Define the condition expression for retrieving records.
ConditionExpression pagecondition = new ConditionExpression();
pagecondition.AttributeName = "address1_stateorprovince";
pagecondition.Operator = ConditionOperator.Equal;
pagecondition.Values.Add("WA");
// Define the order expression to retrieve the records.
OrderExpression order = new OrderExpression();
order.AttributeName = "name";
order.OrderType = OrderType.Ascending;
// Create the query expression and add condition.
QueryExpression pagequery = new QueryExpression();
pagequery.EntityName = "account";
pagequery.Criteria.AddCondition(pagecondition);
pagequery.Orders.Add(order);
pagequery.ColumnSet.AddColumns("name", "address1_stateorprovince", "emailaddress1", "accountid");
// Assign the pageinfo properties to the query expression.
pagequery.PageInfo = new PagingInfo();
pagequery.PageInfo.Count = fetchCount;
pagequery.PageInfo.PageNumber = pageNumber;
// The current paging cookie. When retrieving the first page,
// pagingCookie should be null.
pagequery.PageInfo.PagingCookie = null;
Console.WriteLine("#\tAccount Name\t\t\tEmail Address");while (true)
{
// Retrieve the page.
EntityCollection results = _serviceProxy.RetrieveMultiple(pagequery);
if (results.Entities != null)
{
// Retrieve all records from the result set.
foreach (Account acct in results.Entities)
{
Console.WriteLine("{0}.\t{1}\t\t{2}",
++recordCount,
acct.EMailAddress1,
acct.Name);
}
}
// Check for more records, if it returns true.
if (results.MoreRecords)
{
// Increment the page number to retrieve the next page.
pagequery.PageInfo.PageNumber++;
// Set the paging cookie to the paging cookie returned from current results.
pagequery.PageInfo.PagingCookie = results.PagingCookie;
}
else
{
// If no more records are in the result nodes, exit the loop.
break;
}
}
I have a very strange error with dapper:
there is already an open DataReader associated with this Command
which must be closed first
But I don't use DataReader! I just call select query on my server application and take first result:
//How I run query:
public static T SelectVersion(IDbTransaction transaction = null)
{
return DbHelper.DataBase.Connection.Query<T>("SELECT * FROM [VersionLog] WHERE [Version] = (SELECT MAX([Version]) FROM [VersionLog])", null, transaction, commandTimeout: DbHelper.CommandTimeout).FirstOrDefault();
}
//And how I call this method:
public Response Upload(CommitRequest message) //It is calling on server from client
{
//Prepearing data from CommitRequest
using (var tr = DbHelper.DataBase.Connection.BeginTransaction(IsolationLevel.Serializable))
{
int v = SelectQueries<VersionLog>.SelectVersion(tr) != null ? SelectQueries<VersionLog>.SelectVersion(tr).Version : 0; //Call my query here
int newVersion = v + 1; //update version
//Saving changes from CommitRequest to db
//Updated version saving to base too, maybe it is problem?
return new Response
{
Message = String.Empty,
ServerBaseVersion = versionLog.Version,
};
}
}
}
And most sadly that this exception appearing in random time, I think what problem in concurrent access to server from two clients.
Please help.
This some times happens if the model and database schema are not matching and an exception is being raised inside Dapper.
If you really want to get into this, best way is to include dapper source in your project and debug.
I have the following method which is called from Ajax:
[Authorize]
[ValidateInput(false)]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public JsonNetResult CreateOrUpdateTimeRecord(TimeRecord tr)
{
TimeRecord trLocal;
if (tr.Id == -1 || tr.Id == 0)
{
trLocal = new TimeRecord
{
Description = tr.Description,
StartTime = tr.StartTime,
EndTime = tr.EndTime,
User =new myTimeMvc.Models.NHibernate.Models.User {Id = tr.User.Id},// _userRepo.Get(tr.User.Id),
Hdt = new Hdt {Id = tr.Hdt.Id}//_hdtRepo.Get(tr.Hdt.Id)
};
_timeRepo.Insert(trLocal);
}
else
{
trLocal = _timeRepo.Get(tr.Id);
trLocal.Description = tr.Description;
trLocal.StartTime = tr.StartTime;
trLocal.EndTime = tr.EndTime;
_timeRepo.Update(trLocal);
}
...
}
As you can see my TimeRecord has a reference to User and Hdt. Now I started to work with NHibernate Profiler which complains when I resolve my properties by loading them from their coresponding repositories. Which is clear to me since I actually don't need to query the database for that since I have the ID's for this objects.
User = _userRepo.Get(tr.User.Id),
Hdt = _hdtRepo.Get(tr.Hdt.Id)
But I'm not 100% sure if I can use this instead:
User =new myTimeMvc.Models.NHibernate.Models.User {Id = tr.User.Id},,
Hdt = new Hdt {Id = tr.Hdt.Id}
I guess NHibernate lazy proxies work the same way since they only contain just the ID of the related object and load the rest when it is needed. Do I have to attach this "new" oject anyway to my session?
Can someone tell me what is the correct way to do this?
Cheers,
Stefan
There are a few ways how to achieve that. One of them could be using the Load() method. Check Ayendes post: NHibernate – The difference between Get, Load and querying by id, an extract:
Load will never return null. It will always return an entity or throw an exception. Because that is the contract that we have we it, it is permissible for Load to not hit the database when you call it, it is free to return a proxy instead.
Other words, we can do something like this
User = _userRepo.Load(tr.User.Id),
Hdt = _hdtRepo.Load(tr.Hdt.Id)
Where the Load would be encapsulating the session.Load()