I'm trying to save text fields in MySql using NHibernate in Asp.Net frame work. But while executing this I got the error"Object reference not set to an instance of an object". If anyone knew help me...
Here is the code.
if (!Page.IsPostBack)
{
IList siteList;
ISessionFactory factory = new NHibernate.Cfg.Configuration().Configure().BuildSessionFactory();
using (ISession session = factory.OpenSession())
{
ICriteria sc = session.CreateCriteria(typeof(Employee ));
siteList = sc.List();
session.Close();
}
factory.Close();
}
**Can you post a stack trace? And a description of how you are configuring **
If i had to take a guess the crash is in (because of missing/incorrect configuration information):
new NHibernate.Cfg.Configuration().Configure().Build().SessionFactory()
Related
Im trying to use the MicroOrm.Dapper.Repositories but the usage sample left me hanging on where to get the SqlGenerator object. It's sample documentation is:
public UserRepository(IDbConnection connection, ISqlGenerator<User> sqlGenerator)
: base(connection, sqlGenerator)
{
Amy I using this right:
var conn = new MySqlConnection("connectionStringXYZ");
var generator = new SqlGenerator<User>();
var userRepo = new UserRepository(conn, generator);
which gives me internal server error 500.
You should be able to do:
ISqlGenerator<User> userSqlGenerator = new SqlGenerator<User>(ESqlConnector.MySQL);
Preferably the generator should be a singleton, possibly an injected one.
But your error is an http error, so I suppose you are swallowing the real exception somewhere in your application. Find out the underlying reason.
I use the following RIA Services call to register and return a Project entity.
// On Server; inside RIA Domain Service
[Invoke]
public Project CreateNewProject(String a_strKioskNumber)
{
Decimal dProjectID = ObjectContext.RegisterProjectNumber(a_strKioskNumber)
.FirstOrDefault() ?? -1m;
// Tried this but it returned zero (0)
//int nChanged = ObjectContext.SaveChanges();
var project = (from qProject in ObjectContext.Projects.Include("ProjectItems")
where qProject.ID == dProjectID
select qProject)
.FirstOrDefault();
if (project == null)
return null;
return project;
}
As you can see, it calls a stored procedure that returns a project ID. It uses this ID to look up the Project entity itself and return it. When the Project entity is returned to the client it is detached. I attach it to the DomainContext and modify it.
// At Client
_activeProject = a_invokeOperation.Value; // <-- Detached
_context.Projects.Attach(_activeProject); // <-- Unmodified
if (_activeProject != null)
{
_activeProject.AuthenticationType = "strong"; // <-- Modified
_activeProject.OwnerID = customer.ID;
_projectItems.Do(pi => _activeProject.ProjectItems.Add(pi));
_activeProject.Status = "calculationrequired";
}
At this point it has an entity state of Modified. When I submit changes it gives me an exception regarding a UNIQUE KEY violation as if it is trying to insert it rather than update it.
// At Client
_context.SubmitChanges(OnProjectSaved, a_callback);
I'm using the same DomainContext instance for all operations. Why should this not work?
What's going wrong? This is rather frustrating.
Edits:
I tried this (as suggested by Jeff):
[Invoke]
public void SaveProject(Project a_project)
{
var project = (from qProject in ObjectContext.Projects
where qProject.ID == a_project.ID
select qProject)
.FirstOrDefault();
project.SubmitDate = a_project.SubmitDate;
project.PurchaseDate = a_project.PurchaseDate;
project.MachineDate = a_project.MachineDate;
project.Status = a_project.Status;
project.AuthenticationType = a_project.AuthenticationType;
project.OwnerID = a_project.OwnerID;
project.ProjectName = a_project.ProjectName;
project.OwnerEmail = a_project.OwnerEmail;
project.PricePerPart = a_project.PricePerPart;
project.SheetQuantity = a_project.SheetQuantity;
project.EdgeLength = a_project.EdgeLength;
project.Price = a_project.Price;
project.ShipToStoreID = a_project.ShipToStoreID;
project.MachiningTime = a_project.MachiningTime;
int nChangedItems = ObjectContext.SaveChanges();
}
It did absolutely nothing. It didn't save the project.
What happens if you add a SaveProject method on the server side and send the object back to the server for saving?
I've not done EF with RIA Services, but I've always sent my objects back to the server for saving. I'm assuming that SubmitChanges call you are making wires up everything properly for you for sending it back to the server, but perhaps it is doing something wrong and handling it manually will fix it.
I dont have the source at the moment but I have seen it recommended that you use a new context for each operation in Silverlight. I ran into a similar problem today and it was because I was using a Service level context that was remembering previous values that I didnt want, I changed to creating a new context for each service call and the behavior became what I expected.
public void SaveResponses(ICollection<Responses> items, Action<SubmitOperation> callback)
{
try
{
SurveysDomainContext _context = new SurveysDomainContext();
foreach (Responses item in items)
{
_context.Responses.Add(item);
}
_context.SubmitChanges(callback, null);
}
catch (Exception)
{
throw;
}
}
As for the notion that one can't use a singleton global DomainContext, this is actually debatable. In my project I use a singleton DomainContext with no issues. In other projects, we have created a new DomainContext for different modules in the app where the entities are reused. There are definitely pros and cons. See:
Strategies for Handling Your DomainContext (external blog)
It seems that the problem is that when you attach your project to the DomainContext it checks the _context.Projects entityset and isn't finding an entity with that primary key, and then assumes that the newly attached entity doesn't exist serverside yet and that submitting changes should insert it. A possible workaround might be to explicitly load the newly created Project into the DomainContext. It would ensure that it sets the correct state on the entity--that is, that the project already exists on the server and that that it's an update instance, rather than an insert instance.
So maybe something like:
//after your Project has already been created serverside with the invoke
_context.Load(_context.SomeQueryThatLoadsYourNewlyCreatedProject(), LoadBehavior.RefreshCurrent, (LoadOperation lo) => {
Project project = lo.Entities.FirstOrDefault(); //is attached and has correct state
if (project != null)
{
project.AuthenticationType = "strong";
project.OwnerID = customer.ID;
project.Do(pi => _activeProject.ProjectItems.Add(pi));
project.Status = "calculationrequired";
_context.SubmitChanges(); //hopefully will trigger an update, rather than an insert
}
});
I have a Visual Studio solution with a Silverlight project, and a web project which hosts the Silverlight app. The web project also contains an ASMX web service which is called by the Silverlight ap.
As described below, certain calls to the web service work fine, and yet others cause a CommunicationException to be thrown, wrapping a WebException - both with the message "The server returned the following error: 'not found'".
Firstly, here's my original method, which failed as described above (entity names changed for simplicity):
[WebMethod]
public Customer GetCustomer(int id)
{
CustomerDataContext dc = new CustomerDataContext();
return dc.Customers.SingleOrDefault(x => x.Id == id);
}
Secondly, to debug the problem I took Linq to SQL and the database out of the picture, and the below code worked fine:
[WebMethod]
public Customer GetCustomer(int id)
{
Customer c = new Customer() { ID=1, Name="Bob", History = new EntitySet<CustomerHistory>() };
return c;
}
Third, thinking about this, one difference between the two methods is that the first one would include values in the customer history. I extended the second method to include this, and it started failing again:
[WebMethod]
public Customer GetCustomer(int id)
{
Customer c = new Customer() { ID=1, Name="Bob", History = new EntitySet<CustomerHistory>() };
c.History.Add(new CustomerHistory() { Id=1, CustomerId=1, Text="bla" });
return c;
}
I'm stuck with regards to how to progress - my current thinking is that this could be a deserialization issue on the Silverlight side, when the object graph is deeper. This rationally doesn't make sense, but I can't think of anything else. I've confirmed that the transfer size and buffer size are big enough (2GB by default).
Any pointers would be appreciated.
Ahhhh the famous "Not Found" error, try to get details from that error using the tag in your web.config. That will create a log file providing details of the error.
The following link explains exaclty how to do it :
http://blogs.runatserver.com/lppinson/post/2010/04/15/Debugging-WCF-Web-Services.aspx
Having a lot of problems trying to consume a simple service operator in a WCF Data Service from Silverlight. I've verified the following service operator is working by testing it in the browser:
[WebGet]
public IQueryable<SecurityRole> GetSecurityRolesForUser(string userName) {
string currentUsername = HttpContext.Current.User.Identity.Name;
// if username passed in, verify current user is admin and is getting someone else's permissions
if (!string.IsNullOrEmpty(userName)) {
if (!SecurityHelper.IsUserAdministrator(currentUsername))
throw new DataServiceException(401, Properties.Resources.RequiestDeniedInsufficientPermissions);
} else // else nothing passed in, so get the current user's permissions
userName = currentUsername;
return SecurityHelper.GetUserRoles(userName).AsQueryable<SecurityRole>();
}
However no matter how I try using different methods I've found in various online resources, I've been unable to consume the data. I've tried using the BeginExecute() method on boht the DataServiceContext and DataServiceQuery, but I keep getting errors or no data returned in the EndExecute method. I've got to be doing something simple wrong... here's my SL code:
private void InitUserSecurityRoles() {
MyEntities context = new MyEntities(new Uri("http://localhost:9999/MyService.svc"));
context.BeginExecute<SecurityRole>(new Uri("http://localhost:9999/MyService.svc/GetSecurityRolesForUser"), OnComplete, context);
DataServiceQuery<SecurityRole> query = context.CreateQuery<SecurityRole>("GetSecurityRolesForUser");
query.BeginExecute(OnComplete, query);
}
private void OnComplete(IAsyncResult result) {
OnDemandEntities context = result.AsyncState as OnDemandEntities;
var x = context.EndExecute<SecurityRole>(result);
}
Any tips? I'm at a loss right now on how to properly consume a custom service operator from Silverlight (or even sync using my unit test project) from a OData service. I've also verified via Fiddler that I'm passing along the correct authentication stuff as well, even going to far as explicitly set the credentials. Just to be safe, I even removed the logic from the service operator that does the security trimming.
Got it working thanks to #kaevans (http://blogs.msdn.com/b/kaevans):
private void InitUserSecurityRoles() {
DataServiceContext context = new DataServiceContext(new Uri("http://localhost:9999/MyService.svc"));
context.BeginExecute<SecurityRole>(new Uri("/GetSecurityRolesForUser", UriKind.Relative),
(result) => {
SmartDispatcher.BeginInvoke(
() => {
var roles = context.EndExecute<SecurityRole>(result);
UserSecurityRoles = new List<SecurityRole>();
foreach (var item in roles) {
UserSecurityRoles.Add(item);
}
});
}, null);
}
I had to create the SmartDispatcher because this is happening in a ViewModel. Otherwise I could have just used the static Dispatcher.BeginInvoke(). Couldn't get the roles variable to insert into my UserSecurityRoles (type List) directly for sone reason using various techniques, so I just dropped down to adding it manually (code isn't called often nor is it a collection exceeding more than 10 items max... most are <5).
I’m facing an issue with NHibernate performance and can you please suggest me some optimizations? Below mentioned is a small summary of my application architecture
I have a windows service which is listening to a messaging bus. On receiving a message the service creates an object out of which a property is the received xml snippet and saves the message to the DB (uses NH). There is a WPF UI with a readonly connection to the DB, and on refresh of the UI it displays the objects on the screen.
While the UI does a refresh, it retrieves the xml and deserializes it , from which the object’s properties are derived and binded to the screen.
For example assume an xml XXX is received by the service, it deserializes the xml , creates the book object and save it to the DB and a property/column is SCHEMA which contains the xml snippet.
The UI while refreshed searches all book objects by ID and creates the book objects out of the xml which is being saved (yes, the xml is the constructor param).
Now my issue is that the refresh takes more than 2 minutes to display say 50 book objects. I analyzed it using the NHibernate profiler, and found that the time spend within the DB is negligible, however time spent to create the entities is proportionally huge(10ms:1990 ms).I guess it’s due to the fairly huge size of xml snippet and it’s deserialization.
My question is, how can I improve the performance. I dispose sessions after every refresh and is not lazy loading (please note that the time spend in DB is negligible). On every refresh it’s possible that all objects are updated by some downstream systems or maybe one of them are updated.Can I implement some sort of caching mechanism in this case?
Thanks in advance for any suggestions.
Regards,
-Mike
The entire list of 50 books could be saved in a singleton class meant for caching. Like a cache manager. You could also use say an enterprise library cache but I would suggest an in memory cache. If a book gets added you could update the cache. The cache would have the entire xml so no deserialisation would happen. Also you could update the db in an ansynchronous thread and reduce the time.
Here is the pseudo code
On the service, whenever I receive a message
public void OnMessage(string message)
{
//deserializes the message
DeserializedObject schema = deserializationFactory.Deserialize(message);
var book = new Book(schema,message);
// saves the book using a new session
repository.Save(book);
}
The book object:
public class Book
{
public DeserializedObject Schema{get;set;}
private string xml;
public string Xml{get{return xml;}}
public Book(DeserializedObject schema,string xml):this(schema)
{
this.xml = xml;
}
public Book(DeserializedObject schema):this()
{
this.Schema = schema;
}
public virtual XmlDocument XmlSchema
{
get
{
var doc = new XmlDocument();
if (Schema!= null)
{
var serializer = new XmlSerializer(typeof(DeserializedObject));
var stream = new MemoryStream();
serializer.Serialize(stream, Schema);
stream.Position = 0;
doc.Load(stream);
}
return doc;
}
}
public virtual string SerializedSchema
{
get { return XmlSchema.OuterXml; }
set
{
if (value != null)
Schema = value.Deserialize< DeserializedObject >();
}
}
public string Author
{
get{return Schema.Author;}
}
}
Now the Mapping for Book(uses FNH)
public class BookMap:ClassMap<Book>
{
LazyLoad();
Table("Books");
IdGenerator.Instance.GenerateId(this, "book_id_seq", book => book.Id);
Map(book=> book.SerializedSchema, "SERIALIZED_SCHEMA")
.CustomSqlType("Clob")
.CustomType("StringClob");
}
On UI:
public void OnRefresh()
{
//In reality the call to DB runs on a background worker and the records are binded to the grid after a context switch.
//GetByCriteria creates a new session every time a refresh happens.
datagrid.DataContext = repository.GetByCriteria(ICriterion allBooksforToday);
}
The important thing to note here is Book type is shared between the service and the UI. However, only service can do a write to the DB, wherin the UI can update the trade object (basically the xml) and sends it over the messaging bus (again the xml). The service once receiving it updates the DB.
The xml size will be approximately 20 KB, so that would mean that if I'm loading say 50 books I'll be loading close to an MB of data.
Thanks,-Mike