note

VeloxDB is still in beta and APIs are subject to change. We are in the process of completing the documentation, so some sections may be incomplete or empty at this time.

Class ObjectModel

ObjectModel provides methods for querying the database and creating new objects.

Inheritance

System.Object

ObjectModel

Namespace: VeloxDB.ObjectInterface

Assembly: vlxdb.dll

Syntax

public sealed class ObjectModel : Object

Remarks

ObjectModel provides interface for working with the database. You can use it to fetch objects, create new objects and query indexes. The data provided by the ObjectModel always reflects changes made during the transaction. For example, if you were to create a new object, and then iterate through all objects you would find your newly created object.

For references IsNullable is not enforced during the transaction. That is VeloxDB will allow allow reference with IsNullable set to false to be null during the execution of the database operation. This is done intentionally because sometimes you need a model to be temporarily in invalid state, for example that's the only way to create a circular reference. This check is enforced at the end of database operation, if there is reference that is not nullable with null value at the end of operation, database will rollback transaction and report an error.

VeloxDB stores data in an unmanaged memory. DatabaseObject is just a thin wrapper around this unmanaged memory structure. When you access an object, the database allocates new DatabaseObject and keeps it around for the duration of the transaction. These objects are also used to store changes to the database done during the transaction. This enables VeloxDB to always provide you with the same object no matter how you access it. This also has certain drawbacks, for example when iterating through large amounts of objects (either using GetAllObjects<T>() or by following references) you can end up allocating a lot of objects that VeloxDB will keep around until the transaction is done. If you know that you wont be applying changes to these objects, you can call Abandon() on them. This tells VeloxDB that it doesn't have to keep the reference to the object any more.

This example illustrates how to use Abandon() method.

int count = 0;
// Get cities enumerable.
IEnumerable<City> cities = om.GetAllObjects<City>();

// Iterate over cities
foreach(City city in cities)
{
    // Do your business logic with city.
    if(city.Name.Contains("New"))
    {
        count++;
    }

    // Abandon the object, since we wont be changing it.
    city.Abandon();
}

return count;

Changes done to the objects are kept within ObjectModel. In case of large transactions, these changes can accumulate and negatively affect performance. You can use ApplyChanges() method to apply changes to the database and clear ObjectModel's internal cache's.

Methods

ApplyChanges()

Applies changes accumulated in ObjectModel to the database.

Declaration

public void ApplyChanges()

Remarks

Changes made during the transaction are kept in ObjectModel until the operation ends. These changes as they accumulate can negatively impact ObjectModel performance. ApplyChanges() allows you to apply these changes early. This will clear ObjectModel's caches and can improve performance.

note

Database must be in consistent state when ApplyChanges() is called. If there are any non nullable references that are set to null ApplyChanges() will throw an exception and transaction will be rolled back.

Exceptions

Type	Condition
System.ObjectDisposedException	If ObjectModel has been disposed.

CreateObject<T>()

Create a new object.

Declaration

public T CreateObject<T>()
    where T : DatabaseObject

Returns

Type	Description
T	A new instance of requested type.

Type Parameters

Name	Description
T	Type of object to create.

Remarks

The method creates a new object, which will be committed to the database after the database operation completes. The object is created with all properties set to default values. References are set to null, while simple types are set to DefaultValue if specified, and 0 if not. The Id property is initialized and set to object's Id. This Id can be used to fetch the object from the database.

Exceptions

Type	Condition
System.ObjectDisposedException	If ObjectModel has been disposed.
System.ArgumentException	If requested type is abstract (IsAbstract is true) or If type T is not marked with the DatabaseClassAttribute.

GetAllObjects<T>()

Retrieves all the objects of a given type (or any derived type) from the database.

Declaration

public IEnumerable<T> GetAllObjects<T>()
    where T : DatabaseObject

Returns

Type	Description
System.Collections.Generic.IEnumerable<T>	IEnumerable of all objects of a given type in the database.

Type Parameters

Name	Description
T	Type of objects to get.

Remarks

When used with a base type, GetAllObjects will return all subtypes as well. There is no guarantee for the order of returned objects.

Exceptions

Type	Condition
System.ObjectDisposedException	If ObjectModel has been disposed.
System.ArgumentException	If type T is not marked with theDatabaseClassAttribute

GetHashIndex<T, TKey1>(String)

Get a hash index by name.

Declaration

public HashIndexReader<T, TKey1> GetHashIndex<T, TKey1>(string name)
    where T : DatabaseObject

Parameters

Type	Name	Description
System.String	name	The name of the hash index.

Returns

Type	Description
HashIndexReader<T, TKey1>	Requested hash index

Type Parameters

Name	Description
T	Type for which the hash index is requested.
TKey1	Type of hash index's key.

Exceptions

Type	Condition
System.ArgumentException	If type T is not marked with the DatabaseClassAttribute or if requested hash index is not found.
System.ObjectDisposedException	If ObjectModel has been disposed.

See Also

HashIndexAttribute

HashIndexReader<T, TKey1>

GetHashIndex<T, TKey1, TKey2>(String)

Get hash index with composite key by name.

Declaration

public HashIndexReader<T, TKey1, TKey2> GetHashIndex<T, TKey1, TKey2>(string name)
    where T : DatabaseObject

Parameters

Type	Name	Description
System.String	name	The name of the hash index.

Returns

Type	Description
HashIndexReader<T, TKey1, TKey2>	Requested hash index

Type Parameters

Name	Description
T	Type for which the hash index is requested.
TKey1	Type of hash index's first key.
TKey2	Type of hash index's second key.

Exceptions

Type	Condition
System.ArgumentException	If type T is not marked with the DatabaseClassAttribute or if requested hash index is not found.
System.ObjectDisposedException	If ObjectModel has been disposed.

See Also

HashIndexAttribute

HashIndexReader<T, TKey1, TKey2>

GetHashIndex<T, TKey1, TKey2, TKey3>(String)

Get hash index with composite key by name.

Declaration

public HashIndexReader<T, TKey1, TKey2, TKey3> GetHashIndex<T, TKey1, TKey2, TKey3>(string name)
    where T : DatabaseObject

Parameters

Type	Name	Description
System.String	name	The name of the hash index.

Returns

Type	Description
HashIndexReader<T, TKey1, TKey2, TKey3>	Requested hash index

Type Parameters

Name	Description
T	Type for which the hash index is requested.
TKey1	Type of hash index's first key.
TKey2	Type of hash index's second key.
TKey3	Type of hash index's third key.

Exceptions

Type	Condition
System.ArgumentException	If type T is not marked with the DatabaseClassAttribute or if requested hash index is not found.
System.ObjectDisposedException	If ObjectModel has been disposed.

See Also

HashIndexAttribute

HashIndexReader<T, TKey1, TKey2, TKey3>

GetHashIndex<T, TKey1, TKey2, TKey3, TKey4>(String)

Get hash index with composite key by name.

Declaration

public HashIndexReader<T, TKey1, TKey2, TKey3, TKey4> GetHashIndex<T, TKey1, TKey2, TKey3, TKey4>(string name)
    where T : DatabaseObject

Parameters

Type	Name	Description
System.String	name	The name of the hash index.

Returns

Type	Description
HashIndexReader<T, TKey1, TKey2, TKey3, TKey4>	Requested hash index

Type Parameters

Name	Description
T	Type for which the hash index is requested.
TKey1	Type of hash index's first key.
TKey2	Type of hash index's second key.
TKey3	Type of hash index's third key.
TKey4	Type of hash index's fourth key.

Exceptions

Type	Condition
System.ArgumentException	If type T is not marked with the DatabaseClassAttribute or if requested hash index is not found.
System.ObjectDisposedException	If ObjectModel has been disposed.

See Also

HashIndexAttribute

HashIndexReader<T, TKey1, TKey2, TKey3, TKey4>

GetObject<T>(Int64)

Get object by id.

Declaration

public T GetObject<T>(long id)
    where T : DatabaseObject

Parameters

Type	Name	Description
System.Int64	id	Object's Id.

Returns

Type	Description
T	Returns the queried object if found, otherwise returns null.

Type Parameters

Name	Description
T	The type of object to get.

Exceptions

Type	Condition
System.ObjectDisposedException	If ObjectModel has been disposed.
System.ArgumentException	If type T is not marked with the DatabaseClassAttribute.

GetObjectStrict<T>(Int64)

Get object by id. This is strict version of VeloxDB.ObjectInterface.ObjectModel.GetObject(System.Int64), the difference being that strict version throws an exception if object is not found.

Declaration

public T GetObjectStrict<T>(long id)
    where T : DatabaseObject

Parameters

Type	Name	Description
System.Int64	id	Object's Id.

Returns

Type	Description
T	Returns the queried object if found.

Type Parameters

Name	Description
T	The type of object to get.

Exceptions

Type	Condition
System.ObjectDisposedException	If ObjectModel has been disposed.
System.ArgumentException	If object with given id is not found in the database. or If type T is not marked with the DatabaseClassAttribute.

GetSortedIndex<T, TKey1>(String)

Get a sorted index by name.

Declaration

public SortedIndexReader<T, TKey1> GetSortedIndex<T, TKey1>(string name)
    where T : DatabaseObject

Parameters

Type	Name	Description
System.String	name	The name of the sorted index.

Returns

Type	Description
SortedIndexReader<T, TKey1>	Requested sorted index

Type Parameters

Name	Description
T	Type for which the sorted index is requested.
TKey1	Type of sorted index's key.

Exceptions

Type	Condition
System.ArgumentException	If type T is not marked with the DatabaseClassAttribute or if requested sorted index is not found.
System.ObjectDisposedException	If ObjectModel has been disposed.

See Also

SortedIndexAttribute

SortedIndexReader<T, TKey1>

GetSortedIndex<T, TKey1, TKey2>(String)

Get sorted index with composite key by name.

Declaration

public SortedIndexReader<T, TKey1, TKey2> GetSortedIndex<T, TKey1, TKey2>(string name)
    where T : DatabaseObject

Parameters

Type	Name	Description
System.String	name	The name of the sorted index.

Returns

Type	Description
SortedIndexReader<T, TKey1, TKey2>	Requested sorted index

Type Parameters

Name	Description
T	Type for which the sorted index is requested.
TKey1	Type of sorted index's first key.
TKey2	Type of sorted index's second key.

Exceptions

Type	Condition
System.ArgumentException	If type T is not marked with the DatabaseClassAttribute or if requested sorted index is not found.
System.ObjectDisposedException	If ObjectModel has been disposed.

See Also

SortedIndexAttribute

SortedIndexReader<T, TKey1, TKey2>

GetSortedIndex<T, TKey1, TKey2, TKey3>(String)

Get sorted index with composite key by name.

Declaration

public SortedIndexReader<T, TKey1, TKey2, TKey3> GetSortedIndex<T, TKey1, TKey2, TKey3>(string name)
    where T : DatabaseObject

Parameters

Type	Name	Description
System.String	name	The name of the sorted index.

Returns

Type	Description
SortedIndexReader<T, TKey1, TKey2, TKey3>	Requested sorted index

Type Parameters

Name	Description
T	Type for which the sorted index is requested.
TKey1	Type of sorted index's first key.
TKey2	Type of sorted index's second key.
TKey3	Type of sorted index's third key.

Exceptions

Type	Condition
System.ArgumentException	If type T is not marked with the DatabaseClassAttribute or if requested sorted index is not found.
System.ObjectDisposedException	If ObjectModel has been disposed.

See Also

SortedIndexAttribute

SortedIndexReader<T, TKey1, TKey2, TKey3>

GetSortedIndex<T, TKey1, TKey2, TKey3, TKey4>(String)

Get sorted index with composite key by name.

Declaration

public SortedIndexReader<T, TKey1, TKey2, TKey3, TKey4> GetSortedIndex<T, TKey1, TKey2, TKey3, TKey4>(string name)
    where T : DatabaseObject

Parameters

Type	Name	Description
System.String	name	The name of the sorted index.

Returns

Type	Description
SortedIndexReader<T, TKey1, TKey2, TKey3, TKey4>	Requested sorted index

Type Parameters

Name	Description
T	Type for which the sorted index is requested.
TKey1	Type of sorted index's first key.
TKey2	Type of sorted index's second key.
TKey3	Type of sorted index's third key.
TKey4	Type of sorted index's fourth key.

Exceptions

Type	Condition
System.ArgumentException	If type T is not marked with the DatabaseClassAttribute or if requested sorted index is not found.
System.ObjectDisposedException	If ObjectModel has been disposed.

See Also

SortedIndexAttribute

SortedIndexReader<T, TKey1, TKey2, TKey3, TKey4>

Rollback()

Rollbacks the transaction associated with this instance of ObjectModel class. ObjectModel instance is no longer usable after this.

Declaration

public void Rollback()