I know the title wasn't the greatest, but here is what I actually want to accomplish.
I have a details view that represents Entity1 and its associations. I am capturing the property names and values in a key/value pair. I am currently using reflection to set the Entity properties to the corresponding values for non associations. I doubt this is the most efficient way, but I have been unable to find a better way using Expression Trees. So now I need to set the associations of Entity1 to their corresponding entities based on the primary key of those entity associations, call them Entity2-4.
When iterating the Properties of Entity1, I don't know how to construct a dynamic query to Entity2-4 and set Entity1.association to the corresponding entity. Here is the code I have so far:
foreach (string k in e.Values.Keys)
{
if (e.Values[k] != null && !String.IsNullOrEmpty(e.Values[k].ToString()))
{
System.Type objectType = Entity1.GetType();
PropertyInfo[] p = objectType.GetProperties();
foreach (PropertyInfo pi in p)
{
// set Entity1.Property for non associations (works just fine)
if (pi.Name == k)
{
System.Type t = pi.PropertyType;
pi.SetProperty(e.Values[k].ToString(), Entity1);
break;
}
// when i see pi.Name contain Reference, I know I'm working on an association
else if (pi.Name.Contains("Reference"))
{
// k is in the form of Entity.Property
var name = pi.Name.Left("Reference");
var keys = k.Split('.');
var ent = keys[0];
var prop = keys[1];
if (name == ent)
{
// here I need to obtain an instance from the db
// ie generate my dynamic query to the Entity with the name
// contained within the var "ent"
// I tried using reflection and could instantiate the entity
// but it did me no good as I needed the entity from the db
var entityInstance = some dynamic query;
// here I need to set the association of Entity1 to entityInstance from above
// normally I would use reflection, but I'm not sure that would work
// since EntityReference is the actual property returned by reflection
Entity1.SetAssocation(prop, Entity2);
break;
}
}
}
}
}
EDIT
I basically need construct the entity and its association entities so that I can submit them to the data context. Entity 2 through 4 exist in the db, I need to query the db to obtain the instances to that I may associate them to the new Entity1 I am creating and going to submit.
My basic model:
Entity1
Entity1.ID
Entity1.Prop1
Entity1.Prop2
Entity1.Prop3
Entity1.Entity2
Entity1.Entity3
Entity1.Entity4
Entity2
Entity2.ID
Entity2.Name
Entity3
Entity3.ID
Entity3.Name
Entity4
Entity4.ID
Entity4.Name
We've had an in-depth discussion about how to get the metadata
out of the DbContext
. Here are a few links to get you started. And I'll add some specific comments.
How I can read EF DbContext metadata programmatically?
A short summary (but you should check in there for more):
using (var db = new MyDbContext())
{
var objectContext = ((IObjectContextAdapter)db).ObjectContext;
var container = objectContext.MetadataWorkspace.GetEntityContainer(objectContext.DefaultContainerName, DataSpace.CSpace);
var dependents = ((EntitySet)(set)).ForeignKeyDependents;
var principals = ((EntitySet)(set)).ForeignKeyPrincipals;
var navigationProperties = ((EntityType)(set.ElementType)).NavigationProperties;
// and e.g. for many-to-many (there is more for other types)
ManyToManyReferences = navigationProperties.Where(np =>
np.FromEndMember.RelationshipMultiplicity == RelationshipMultiplicity.Many &&
np.ToEndMember.RelationshipMultiplicity == RelationshipMultiplicity.Many)
.Select(np => Extensions.CreateLambdaExpression<TEntity>(np.Name))
.ToList();
}
@Goran Obradovic did a great job to wrap up what I started into a set of reusable queries (my due credits to him:).
I have worked out all other sorts of information that's in there. This is just for the DataSpace.CSpace
(which is the most useful to you), but there is also DataSpace.SSpace
etc. - which are more for creating SQL queries etc. I'll put most links at the bottom.
guess
here what's the direction that you're heading)
db.Set<Worker>().Find(1);
Is the generic method for accessing DbSet
for a specific entity.
You could also construct it from a Type
if you need it to be fully dynamic, e.g....
(I always wanted to do this:)
MethodInfo setMethod = typeof(DbContext).GetMethod("Set", new Type[]{});
MethodInfo genericSetMethod = setMethod.MakeGenericMethod(new Type[] { typeof(YourEntity) });
var set = genericSetMethod.Invoke(db, new object[] {});
Put your entity - or your Type
instead of typeof(YourEntity)
.
You could then proceed and query that for e.g. Find(id)
- for that entity - to get concrete values etc.
That's as dynamic as it gets - I'm not sure if that's what you want - but I'm just throwing things out here in case you need it.
That should get you started at least I hope.