this is my Model:
public class UserDetails
{
public string UserName { get; set; }
public virtual Category Category { get; set; }
}
this is my query to fetch user details along with category:
var data = (from temp in context.UserDetails.Include("Category") select temp).OrderBy(c => c.UserId);
this is how i am accessing on controller:
List<UserDetails> staffDetails = staffBal.fetchStaffDetails();
var categoryModel = new CategoryModel();
Data = staffDetails.Select(x =>
{
var userDetailModel = new UserDetailsModel();
userDetailModel.UserId = x.UserId;
userDetailModel.FName = x.FName;
categoryModel.CategoryName = x.Category.Name;//i am getting error on this line.object reference not set to instance of object
can anybody tell me what is the solution???
You say in your comment: for some records it is coming null for some records it is not null meaning that x.Category is null. Therefore, any attempt to access x.Category.Name will fail. Change the line to this:
categoryModel.CategoryName = x.Category == null ? "" : x.Category.Name;
Related
All of my entities (that are mapped to a database table) inherit from an entity class with a dynamic component on it called Attributes e.g.:
public abstract class Entity<T> {
public virtual T Id { get; set; }
private IDictionary _attributes;
public virtual IDictionary Attributes {
get { return _attributes ?? (_attributes = new Hashtable()); }
set { _attributes = value; }
}
}
The Attributes collection allows me to add extra fields to each entity without directly changing the entity itself. This allows me to make my application more modular.
For example say I have the following entity:
public class User : Entity<int> {
public virtual string Name { get; set; }
}
Now say I have a Forum module which needs a NumPosts property against the User. I would add the field against the Users table in the database. This field is non nullable and has a default value of 0. I then map the field using the dynamic component against the User entity.
However when I try inserting the user by saying:
session.Save(new User() { Name = "Test" });
It throws an error as it's expecting me to set a value for NumPosts and the generated SQL would be something like:
INSERT INTO Users (Name, NumPosts) VALUES ('Test', NULL)
However NumPosts does not allow nulls and hence the error. Ideally I'd like it to say the following if the Attributes collection does not contain an entry for NumPosts:
INSERT INTO Users (Name) VALUES ('Test')
An alternative is to say the following which would work fine:
session.Save(new User() { Name = "Test", Attributes = new Hashtable() { { "NumPosts", 0 } } });
The problem I have is that I don't want the modules to have a dependency on each other and I can't really say this.
For reference here's a bare bones version of session factory method which maps the NumPosts field:
return Fluently.Configure()
...
.ExposeConfiguration(c => {
// Get the persistent class
var persistentClass = c.GetClassMapping("User");
// Create the attributes component
var component = new Component(persistentClass);
// Create a simple value
var simpleValue = new SimpleValue(persistentClass.Table);
// Set the type name
simpleValue.TypeName = "Int32";
// Create a new db column specification
var column = new Column("NumPosts");
column.Value = simpleValue;
column.Length = 10;
column.IsNullable = false;
column.DefaultValue = "0";
// Add the column to the value
simpleValue.AddColumn(column);
// Ad the value to the component
component.AddProperty(new Property() { Name = column.Name, Value = simpleValue });
// Add the component property
persistentClass.AddProperty(new Property() { Name = "Attributes", Value = component });
})
.BuildConfiguration();
I'd appreciate if someone could let me know if this is possible. Thanks
You know how to make it working as described above:
... An alternative is to say the following which would work fine:
session.Save(new User()
{
Name = "Test", Attributes = new Hashtable() { { "NumPosts", 0 } }
});
... The problem I have is that I don't want the modules to have a dependency on each other and I can't really say this...
In case, that the biggest issue is the explicit Attributes initialization ("...I don't want the modules to have a dependency...") we can use:
12.2. Event system
So, with Listener like this:
[Serializable]
public class MyPersistListener : NHibernate.Event.ISaveOrUpdateEventListener
{
public void OnSaveOrUpdate(SaveOrUpdateEvent #event)
{
var entity = #event.Entity as Entity<int>; // some interface IHaveAttributes
if (entity == null) // would be more appropriate
{
return;
}
var numPosts = entity.Attributes["NumPosts"] as int?;
if (numPosts.HasValue)
{
return;
}
entity.Attributes["NumPosts"] = 0;
}
}
Based on this doc snippet:
Configuration cfg = new Configuration();
ILoadEventListener[] stack = new ILoadEventListener[] { new MyLoadListener(), new DefaultLoadEventListener() };
cfg.EventListeners.LoadEventListeners = stack;
This should be the init in our case:
.ExposeConfiguration(c => {
var stack = new ISaveOrUpdateEventListener [] { new MyPersistListener() };
c.EventListeners.SaveEventListeners= stack;
I have following two Collections in RavenDB.Please help me for creating index for getting data from both collection.
public class Ticket
{
public string TicketID{get;set;}
public double Total{get;set;}
}
public class ImportTiming
{
public string Id{get;set;}
public DateTime ExtractTime{get;set;}
}
AND
public class ResultClass
{
public string TicketID{get;set;}
public double Total{get;set;}
public DateTime ExtractTime{get;set;}
}
TicketID(Ticket) & Id(ImportTiming) are same.I am using LoadDocument for ExtractTime but it is showing NULL value.
Thanks in advance!!!
Finally i got solution...
Bellow is the Map-Reduce function,in which i have used LoadDocument<> for selecting data from ImportTiming Document.
public class IdxJoinBetweenCollections : AbstractIndexCreationTask<Ticket,JoinBetweenCollections.ResultClass>
{
public IdxJoinBetweenCollections()
{
Map = docs => from doc in docs
let TimeDoc = LoadDocument<ImportTiming>("ImportTiming/" + doc.TicketID)
select new
{
ID = doc.TicketID,
Total = doc.Total,
ExtractTime = TimeDoc.ExtractComplete,
};
Reduce = results => from res in results
group res by res.ID into g
select new
{
ID = g.Key,
Total = g.Select(x => x.Total).FirstOrDefault(),
ExtractTime = g.Select(x => x.ExtractTime).FirstOrDefault(),
};
}
}
In LoadDocument("ImportTiming/" + doc.TicketID),i have used CollectionName followed by Id so that i gets whole document.If i dont use CollectionName then it shows NULL value.
Reference:http://ravendb.net/docs/2.0/client-api/querying/static-indexes/indexing-related-documents
Background
I'm attempting to use ServiceStack.OrmLite to grab some values (so I can cache them to run some processing against them).
I need to grab a combination of three values, and I have a custom SQL statement that will yield them (does the joins, etc.)
Because this will be a large list of combinations, I'd like to pass in some lists of values and use Sql.In to filter to only the results that have those values.
Specifics
I need to check whether an invoice is unique to a firm and another value (called ClaimLawsuitID here).
so have my poco:
public class FirmIDClaimLawsuitIDInvoiceNumberCombination
{
public string FirmID { get; set; }
public string ClaimLawsuitID { get; set; }
public string InvoiceNumber { get; set; }
}
and I have my SQL statement:
select tblDefenseInvoice.FirmID, tblDefInvClaimantDetail.ClaimLawsuitID, tblDefInvClaimantDetail.invoiceNumber
from tblDefenseInvoice
inner join tblDefInvClaimantDetail
on(tblDefenseInvoice.DefenseInvoiceID = tblDefInvClaimantDetail.DefenseInvoiceID)
I would like to run the following:
public List<FirmIDClaimLawsuitIDInvoiceNumberCombination> GetFirmIDClaimLawsuitIDInvoiceNumberCombinationsForExistingItems(IEnumerable<int> firmIds, IEnumerable<long> claimLawsuitIDs, IEnumerable<string> invoiceNumbers)
{
var sql = #"select tblDefenseInvoice.FirmID, tblDefInvClaimantDetail.ClaimLawsuitID, tblDefInvClaimantDetail.invoiceNumber
from tblDefenseInvoice
inner join tblDefInvClaimantDetail
on(tblDefenseInvoice.DefenseInvoiceID = tblDefInvClaimantDetail.DefenseInvoiceID)";
var ev = OrmLiteConfig.DialectProvider.ExpressionVisitor<tblClaimLawsuit>();
var firmFilter = PredicateBuilder.True<tblDefenseInvoice>();
var claimLawsuitFilter = PredicateBuilder.True<tblDefInvClaimantDetail>();
var invoiceNumberFilter = PredicateBuilder.True<tblDefInvClaimantDetail>();
firmFilter = x => Sql.In(x.FirmID, firmIds);
claimLawsuitFilter = x => Sql.In(x.ClaimLawsuitID, claimLawsuitIDs);
invoiceNumberFilter = x => Sql.In(x.InvoiceNumber, invoiceNumbers);
ev.Select(sql);
ev.Where(firmFilter);
ev.Where(claimLawsuitFilter);
ev.Where(invoiceNumberFilter);
return dal.DB.Select<FirmIDClaimLawsuitIDInvoiceNumberCombination>(ev.ToSelectStatement());
}
Question
Is this possible to achieve this way?
Is there some other way of achieving this within ServiceStack's OrmLite that is cleaner and I'm unaware of?
Since I was selecting to a POCO, I simply needed to add the filters based on that POCO.
The following worked just fine:
public List<FirmIDClaimLawsuitIDInvoiceNumberCombination>
GetFirmIDClaimLawsuitIDInvoiceNumberCombinationsForExistingItems(
IEnumerable<long> firmIds,
IEnumerable<long> claimLawsuitIDs)
{
var sql = #"select tblDefenseInvoice.FirmID, tblDefInvClaimantDetail.ClaimLawsuitID, tblDefInvClaimantDetail.invoiceNumber
from tblDefenseInvoice
inner join tblDefInvClaimantDetail
on(tblDefenseInvoice.DefenseInvoiceID = tblDefInvClaimantDetail.DefenseInvoiceID)";
var ev = OrmLiteConfig.DialectProvider.ExpressionVisitor<FirmIDClaimLawsuitIDInvoiceNumberCombination>();
var firmFilter = PredicateBuilder.True<FirmIDClaimLawsuitIDInvoiceNumberCombination>();
var claimLawsuitFilter = PredicateBuilder.True<FirmIDClaimLawsuitIDInvoiceNumberCombination>();
firmFilter = x => Sql.In(x.FirmID, firmIds);
claimLawsuitFilter = x => Sql.In(x.ClaimLawsuitID, claimLawsuitIDs);
ev.Select(sql);
ev.Where(firmFilter);
ev.Where(claimLawsuitFilter);
return dal.DB.Select<FirmIDClaimLawsuitIDInvoiceNumberCombination>(ev.ToSelectStatement());
}
If I want single primitive value like int, string, float etc I can do like this.
using (var db = new SQLiteConnection(DbPath))
{
double i = db.CreateCommand("select salary from PersonMaster where personId = ?", 9).ExecuteScalar<double>();
}
If I try to return whole object of person master i.e. single row the below code returns null
using (var db = new SQLiteConnection(DbPath))
{
PersonMaster objPersonMaster = db.CreateCommand("select * from PersonMaster where personId = ?", 9).ExecuteScalar<PersonMaster>();
}
I compulsory have to use this
using (var db = new SQLiteConnection(DbPath))
{
List<PersonMaster> lstPersonMaster = db.Query<PersonMaster>("select * from PersonMaster where personId = ?", 9);
PersonMaster objPersonMaster = lstPersonMaster.First();
}
Is there any way to get single row as object, rather than dealing with List<T>
I am assuming you are using SQLite-Net. If that is the case you can use the Find method. Find gets an object using its primary key.
The personId field needs the PrimaryKey attribute as follows:
public class PersonMaster
{
[PrimaryKey]
public int personId { get; set; }
public string name { get; set; }
public decimal salary { get; set; }
}
Then you can use Find like so:
// get person 9
PersonMaster person9 = db.Find<PersonMaster>(9);
You can either use "TOP(1) yourquery" or "yourquery LIMIT 1"
if you just want to get rid of the list step, you can do it directly:
PersonMaster objPersonMaster = db.Query<PersonMaster>("select * from PersonMaster where personId = ?", 9).First();
Of course you have to deal with a possible exception in case nothing is returned, but you should do this also with the list approach anyway.
I'm a new user in LINQ to SQL and I have some problems using it.
I've used LINQ to SQL Designer and I have created my classes, mapped on the DB tables.
In particular, I have one class, named voice:
[global::System.Data.Linq.Mapping.TableAttribute(Name="dbo.voce")]
public partial class voce : INotifyPropertyChanging, INotifyPropertyChanged
{
private static PropertyChangingEventArgs emptyChangingEventArgs = new PropertyChangingEventArgs(String.Empty);
private int _id_voce;
... other private fields;
private int _category;
private EntityRef<category> _category1;
public voce()
{
this._riepilogo = new EntitySet<riepilogo>(new Action<riepilogo>(this.attach_riepilogo), new Action<riepilogo>(this.detach_riepilogo));
this._hera = default(EntityRef<hera>);
this._category1 = default(EntityRef<category>);
OnCreated();
}
[global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_id_voce", AutoSync=AutoSync.OnInsert, DbType="Int NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)]
public int id_voce
{
get
{
return this._id_voce;
}
set
{
if ((this._id_voce != value))
{
this.Onid_voceChanging(value);
this.SendPropertyChanging();
this._id_voce = value;
this.SendPropertyChanged("id_voce");
this.Onid_voceChanged();
}
}
}
......
[global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_category", DbType="Int NOT NULL")]
public int category
{
get
{
return this._category;
}
set
{
if ((this._category != value))
{
if (this._category1.HasLoadedOrAssignedValue)
{
throw new System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException();
}
this.OncategoryChanging(value);
this.SendPropertyChanging();
this._category = value;
this.SendPropertyChanged("category");
this.OncategoryChanged();
}
}
}
As you can see, voce class has a field named category that refers to a table named category.
When I add a new voce to my database, I create a new voce istance and, using the DataContext, i simply add it, using:
voce v = new voce(){...field, category1 = //create or retrieve category};
In particular, the category field is retrieved from the DB if already exists or, if not, it is inserted, before I insert the voice.
The problem is that when I add the voice in the database:
datacontext.InsertOnSubmit(v);
datacontext.SubmitChanges();
it inserts the category again, failing with the unique contraint.
How can I add a voice without adding every nested object?
Thank you and sorry for my bad English.
internal category GetCategoryFromDescription (string desc, Utility.VOICE_MODALITY mode)
{
bool type = mode == Utility.VOICE_MODALITY.ENTRATA ? true : false;
var query = from cat in dc.category
where cat.description == desc && cat.type == type
select cat;
if (query.Count() == 0)
{
category newC = new category() { description = desc };
dc.category.InsertOnSubmit(newC);
dc.SubmitChanges();
return newC;
}
else
return query.Single();
}