Object Relational Mapping#

Simple object-relational mapping abstraction layer for geodatabase feature classes and tables. It converts features and rows into a (lazy) sequence of strongly-typed objects.

Getting Started#

You can begin using the object-relational mappping in 2 easy steps.

  1. Create a class that inherits from the Entity class.

    • Decorate each property in the class with the EntityField attribute that you want to be mapped to column on a table.
      • The data type of the property should match that of the table column.
    • Decorate the class with the EntityTable attribute that you want to have mapped to a table.

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    [EntityTable("CITY")]
public class City : Entity
{
    [EntityField("NAME")]
    public string Name {get;set;}

    [EntityField("POPULATION")]
    public int? Population {get;set;}

    [EntityField("STATE")]
    public string State {get;set;}

    [EntityField("DESCRIPTION")]
    public string Description {get;set}
}
    2. Use the CRUD extension methods that have been exposed on the ITable and IFeatureClass interfaces and Entity class.

CRUD#

An entity object can be used to C-reate, R-ead, U-pdate and D-elete either IRow or IFeature objects by using methods exposed on the Entity object or (ITable and IFeatureClass) interfaces.

  1. Create: Create new records using entity objects.

    Class Method Description
    Entity Insert(ITable) Inserts the entity object into the table using an insert cursor.
    Entity Insert(IFeatureClass) Inserts the entity object into the feature class using an insert cursor. 

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    var cities = workspace.GetTable(typeof(City));
var denver = new City
{
    Name = "Denver",
    Population = 663862,
    State = "Colorado",
    Description = "The capital of Colorado."
};

denver.Insert(cities);
    2. Read: Load data from a table into entity objects.

    Interface Method Description
    ITable Map(IQueryFilter) Reads the database rows as a (lazily-evaluated) sequence of objects that are converted into the entity type.
    IFeatureCLass Map(IQueryFilter) Reads the database features as a (lazily-evaluated) sequence of objects that are converted into the entity type. 

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    var filter = new QueryFilter();
filter.Where = "State = 'Colorado';

var cities = workspace.GetTable(typeof(City));
foreach (var city in cities.Map<City>(filter)
{
    Console.WriteLine("Name: {0}" , city.Name);
    Console.WriteLine("POP: {0}" , city.Population);
    Console.WriteLine("State: {0}" , city.State);
    Console.WriteLine("Description : {0}", city.Description);
}
    3. Update: Flush property changes to the underlying row in the database.

    Class Method Description
    Entity Update() Updates the underlying backing object (either IRow or IFeature) 
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    var cities = workspace.GetTable(typeof(City));
var filter = new QueryFilter();
filter.Where = "Name = 'Denver'";

var denver = cities.Map<City>(filter).SingleOrDefault();
denver.Description = "Denver, the capital of Colorado, is an American metropolis dating to the Old West era. Larimer Square, the city’s oldest block, features landmark 19th-century buildings.";
denver.Update();

  2. Delete: Remove records from the table using the entity object.

    Class Method Description
    Entity Delete() Deletes the underlying backing object (either IRow or IFeature) 
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    var cities = workspace.GetTable(typeof(City));
var filter = new QueryFilter();
filter.Where = "Name = 'Denver'";

var denver = cities.Map<City>(filter).SingleOrDefault();
denver.Delete();
denver = null;