NHibernate.MappingException: No persister for: XYZ

Question

Now, before you say it: I did Google and my hbm.xml file is an Embedded Resource.

Here is the code I am calling:

ISession session = GetCurrentSession();
var returnObject =  session.Get<T>(Id);

Here is my mapping file for the class:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
  <class name="HQData.Objects.SubCategory, HQData" table="SubCategory" lazy="true">
    <id name="ID" column="ID" unsaved-value="0">
      <generator class="identity" />
    </id>

    <property name="Name" column="Name" />
    <property name="NumberOfBuckets" column="NumberOfBuckets"  />
    <property name="SearchCriteriaOne" column="SearchCriteriaOne" />

    <bag name="_Businesses" cascade="all">
      <key column="SubCategoryId"/>
      <one-to-many 
         class="HQData.Objects.Business, HQData"/>
    </bag>

    <bag name="_Buckets" cascade="all">
      <key column="SubCategoryId"/>
      <one-to-many
         class="HQData.Objects.Bucket, HQData"/>
    </bag>

  </class>
</hibernate-mapping>

Has anyone run to this issue before?

Here is the full error message:

MappingException: No persister for:  HQData.Objects.SubCategory]NHibernate.Impl.SessionFactoryImpl.GetEntityPersister(String entityName, Boolean throwIfNotFound)
 in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionFactoryImpl.cs:766 NHibernate.Impl.SessionFactoryImpl.GetEntityPersister(String entityName)
 in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionFactoryImpl.cs:752 NHibernate.Event.Default.DefaultLoadEventListener.OnLoad(LoadEvent event, LoadType loadType)
 in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Event\Default\DefaultLoadEventListener.cs:37 NHibernate.Impl.SessionImpl.FireLoad(LoadEvent event, LoadType loadType)
 in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionImpl.cs:2054 NHibernate.Impl.SessionImpl.Get(String entityName, Object id)
 in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionImpl.cs:1029 NHibernate.Impl.SessionImpl.Get(Type entityClass, Object id)
 in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionImpl.cs:1020 NHibernate.Impl.SessionImpl.Get(Object id)
 in c:\CSharp\NH2.0.0\nhibernate\src\NHibernate\Impl\SessionImpl.cs:985 HQData.DataAccessUtils.NHibernateObjectHelper.LoadDataObject(Int32 Id)
 in C:\Development\HQChannelRepo\HQ Channel Application\HQChannel\HQData\DataAccessUtils\NHibernateObjectHelper.cs:42 HQWebsite.LocalSearch.get_subCategory()
 in C:\Development\HQChannelRepo\HQ Channel Application\HQChannel\HQWebsite\LocalSearch.aspx.cs:17 HQWebsite.LocalSearch.Page_Load(Object sender, EventArgs e)
 in C:\Development\HQChannelRepo\HQ Channel Application\HQChannel\HQWebsite\LocalSearch.aspx.cs:27 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +15 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +33 System.Web.UI.Control.OnLoad(EventArgs e) +99 System.Web.UI.Control.LoadRecursive() +47 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1436

Update, here's what the solution for my scenario was: I had changed some code and I wasn't adding the Assembly to the config file during runtime.

I had the same error, but a different issue. Session.Load("SearchItem",searchItemID) as SearchItem returns a mapping error, Session.Load(searchItemID) does not (and is a less error prone way of doing it anyway. — Kendrick, Aug 10 '10 at 19:31

score 101 · Accepted Answer · answered Sep 12 '08 at 00:20

101

Sounds like you forgot to add a mapping assembly to the session factory configuration..

If you're using app.config...

.
.
    <property name="show_sql">true</property>
    <property name="query.substitutions">true 1, false 0, yes 'Y', no 'N'</property>
    <mapping assembly="Project.DomainModel"/>  <!-- Here -->
</session-factory>
.
.

answered Sep 12 '08 at 00:20

Andy S

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How to do this in Fluent NHibernate, i'm developing a pattern in a serperate project, so i don't have access to the user assembly? – Mustafa Magdy Jan 14 '11 at 00:22
If you can't reference the user assembly, I don't think you'll be able to use Fluent NHibernate. – Andy S Jan 18 '11 at 17:24

score 99 · Answer 2 · answered Nov 25 '09 at 10:09

99

Something obvious, yet quite useful for someone new to NHibernate.

All XML Mapping files should be treated as Embedded Resources rather than the default Content. This option is set by editing the Build Action attribute in the file's properties.

XML files are then embedded into the assembly, and parsed at project startup during NHibernate's configuration phase.

answered Nov 25 '09 at 10:09

Chris Vosnidis

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Haleluia, I has it as an `Embedded resource`, but when I copied it from one computer to another, the file lost this property. I scratched my head for a couple of good minutes. – Dragos Durlut Jun 02 '11 at 21:43
1

@DragosDurlut the project file (.csproj) that saves the information of project files, not the file itself. – Wagner Leonardi Sep 04 '14 at 17:31

score 56 · Answer 3 · answered Aug 18 '10 at 13:45

56

My issue was that I forgot to put the .hbm in the name of the mapping xml. Also make sure you make it an embedded resource!

answered Aug 18 '10 at 13:45

nHibernate User

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That was my mistake too! – Gringo Jul 25 '14 at 15:50
This was my problem also, get the same error as in Q when doing get. When trying to query all of the objects of that type, no error, just an empty result set! – Christoph May 18 '15 at 15:34
Arg--forgot the .hbm too. Thanks! – Dr. Hilarius Apr 19 '16 at 16:29
Nice, I've forgotten to switch build action to the embedded resource. – LaoR Jun 18 '21 at 12:05

score 47 · Answer 4 · edited Jan 14 '15 at 16:13

47

I got this off of here:

In my case the mapping class was not public. In other words, instead of:

public class UserMap : ClassMap<user>  // note the public!

I just had:

class UserMap : ClassMap<user>

edited Jan 14 '15 at 16:13

Benjamin Hodgson

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answered Aug 22 '10 at 16:14

basarat

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Thanks, you just saved me from a bit of a headache. :) – Rytmis Oct 20 '10 at 08:37
2

If you're using Fluent, I'd say this would be the more common cause. Thanks, that was very easy to miss. – Richard Neil Ilagan Mar 08 '11 at 15:19
1

Thanks! In going to check whether I'd made my mapping classes public or not I discovered I hadn't written a mapping class for this entity - oops!! :) Saved me heaps of time!! – Jen Mar 31 '11 at 05:54
you saved me a couple of hours, thanks a lot – Igor Feb 11 '22 at 12:37

Nickmaovich · Answer 5 · 2019-04-24T13:27:09.613

30

Spending about 4 hours on googling and stackoverflowing, trying all of stuff around there, i've found my error:

My mapping file was called .nbm.xml instead of .hbm.xml. That was insane.

edited Apr 24 '19 at 13:27

answered Aug 01 '12 at 11:27

Nickmaovich

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Argh, just did the same except i had it just as .xml instead of .hbm.xml. Maybe there should be some hints in the errors :) – Rezler Aug 08 '12 at 14:16
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omg. I cannot believe I did this. I was searching for hours in mapping files for errors and it turns out I had made a typo in the filename... doh. Thank you! I shudder to think how long I would have been tearing my hair out for if I hadn't stumbled across this. – kamui Apr 08 '13 at 08:35
1

Wow, great catch - I was pulling my hair out on this problem. Looked over my xml file a hundred times and couldn't figure out why it wasn't working like the others. I was actually missing the ".hbm" part of the file name. Thanks! – Winger Apr 18 '14 at 22:20
1

You saved my hours. Thanks – Manjay_TBAG Aug 27 '19 at 14:24

score 4 · Answer 6 · answered Jul 08 '10 at 13:04

I had similar problem, and I solved it as folows:

I working on MS SQL 2008, but in the NH configuration I had bad dialect: NHibernate.Dialect.MsSql2005Dialect if I correct it to: NHibernate.Dialect.MsSql2008Dialect then everything's working fine without a exception "No persister for: ..." David.

score 3 · Answer 7 · answered Jun 28 '12 at 21:09

3

To add to Amol's answer, don't make the mistake of specifying the Interface class type. Make sure you specify the implementation class. (Ie. don't use IDomainObjectType). Not that I made this mistake... :)

answered Jun 28 '12 at 21:09

goku_da_master

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score 3 · Answer 8 · answered Dec 27 '10 at 10:54

3

I had the same problem because I was adding the wrong assembly in Configuration.AddAssembly() method.

answered Dec 27 '10 at 10:54

IdontCareAboutReputationPoints

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score 3 · Answer 9 · answered May 24 '11 at 15:13

I was also adding the wrong assembly during initialization. The class I'm persisting is in assembly #1, and my .hbm.xml file is embedded in assembly #2. I changed cfg.AddAssembly(... to add assembly #2 (instead of assembly #1) and everything worked. Thanks!

score 2 · Answer 10 · answered Apr 18 '14 at 11:59

2

This error occurs because of invalid mapping configuration. You should check where you set .Mappings for your session factory. Basically search for ".Mappings(" in your project and make sure you specified correct entity class in below line.

.Mappings(m => m.FluentMappings.AddFromAssemblyOf<YourEntityClassName>())

answered Apr 18 '14 at 11:59

Arkadas Kilic

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thanks dude! I switched the project my entities were sitting in! – viggity Sep 29 '15 at 20:49

score 2 · Answer 11 · answered Sep 11 '08 at 23:01

2

Should it be name="Id"? Typos are a likely cause.

Next would be to try it out with a non-generic test to make sure you're passing in the proper type parameter.

Can you post the entire error message?

answered Sep 11 '08 at 23:01

Matt Hinze

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score 1 · Answer 12 · answered Mar 10 '10 at 23:56

1

Don't forget to specify mapping information in .config file

e.g.

where MyApp.Data is assembly that contains your mappings

answered Mar 10 '10 at 23:56

score 1 · Answer 13 · answered Mar 05 '09 at 15:04

If running tests on the repository from a seperate assembly, then make sure your Hibernate.cfg.xml is set to output always in the bin directory of said assembly. This wasn't happening for us and we got the above error in certain circumstances.

Disclaimer: This might be a slightly esoteric bit of advice, given that it's a direct result of how we structure our repository integration test assemblies (i.e. we have a symbolic link from each test assembly to a single Hibernate.xfg.xml)

score 0 · Answer 14 · answered Mar 02 '20 at 14:07

I have a similar problem but all mentioned requirements are met. In my case I try to save some entity class (Type of OBJEKTE) back to the DB. Other places do work but only in this case it fails and raises this exception.

My solution (HACK) was to re-map the objet of type OBJEKTE again and store it then. Suddenly it works. But don't ask why.

            OBJEKTE t = _mapper.Map<OBJEKTE>(inparam);
            OBJEKTE res = await _objRepo.UpdateAsync(t);

If inparam would go straight to UpdateAsync() it cannot find a matching persistor.

It could be explained by the way NH does this. It derives a proxy from your mapping class and implements the properties with dirty handling included. See this:

t.GetType()
{Name = "OBJEKTE" FullName = "MyComp.Persistence.OBJEKTE"}

inparam.GetType()
{Name = "OBJEKTEProxyForFieldInterceptor" FullName = "OBJEKTEProxyForFieldInterceptor"}

The fun thing though is that the source of inparam is in fact the NH repository itself. Anyways. I stay with this reassign hack for the next time being.

score 0 · Answer 15 · answered Dec 09 '20 at 14:22

I my case I fetched an entity without await:

var company = _unitOfWork.Session.GetAsync<Company>(id);

and then I tried to delete it:

await _unitOfWork.Session.DeleteAsync(company);

I could not decipher the error message that I'm deleting a Task<Company> instead of Company:

MappingException: No persister for: System.Runtime.CompilerServices.AsyncTaskMethodBuilder'1+AsyncStateMachineBox'1[[SmartGuide.Core.Domain.Users.Company, SmartGuide.Core, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null],[NHibernate.Impl.SessionImpl+d__54`1[[SmartGuide.Core.Domain.Users.Company, SmartGuide.Core, Version=2.0.0.0, Culture=neutral, PublicKeyToken=null]], NHibernate, Version=5.3.0.0, Culture=neutral, PublicKeyToken=aa95f207798dfdb4]]

score 0 · Answer 16 · edited Apr 28 '10 at 05:18

0

Had a similar problem when find an object by id... All i did was to use the fully qualified name in the class name. That is Before it was :

find("Class",id)

Object so it became like this :

find("assemblyName.Class",id)

edited Apr 28 '10 at 05:18

Jeff Atwood

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answered Mar 18 '09 at 21:05

score 0 · Answer 17 · answered Feb 22 '22 at 20:42

You would think that after 14 years, all possible answers to this question have been written down. It seems like that is not the case.

In the application I'm currently working on, there are several ISessionFactory instances, each one for a different database.

If you're taking the wrong one to create your ISession, of course it will have no idea of the class you're trying to persist, which was the error in my case.

score 0 · Answer 18 · edited May 24 '17 at 01:33

0

Make sure you have called the CreateCriteria(typeof(DomainObjectType)) method on Session for the domain object which you intent to fetch from DB.

edited May 24 '17 at 01:33

RBT

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answered Sep 09 '11 at 10:05

Amol

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This is a persist, not a fetch. – Joshua Drake May 23 '17 at 20:13

NHibernate.MappingException: No persister for: XYZ

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