Get Navigation Properties of given EntityType

Question

I am using VS2010, EF4.0. Need function like the following.

private string[] GetNaviProps(Type entityType)//eg typeof(Employee)
{
    NorthwindEntities en = new NorthwindEntities();
    //here I return all Properties only for example
    return entityType.GetProperties().Select(p=>p.Name).ToArray();
    //should return Orders,Territories...
}

I have checked this, but IObjectContextAdapter seems something in EF6.0 and .net4.5. I tried to replace it like

var workspace = en.MetadataWorkspace;

So it can compile, but exception throw at the 3nd line then.
Any help?

Answer 1

You can filter GetProperties results to get only these which implement ICollection or IEnumerable. However, you should remember that string implements IEnumerable, so you have to add additional check not to return string properties.

return entityType.GetProperties()
                 .Where(p => typeof(IEnumerable).IsAssignableFrom(p.PropertyType) && p.PropertyType != string)
                 .Select(p => p.Name)
                 .ToArray();

Update

You can change you Where predicate to compare namespaces as well. It returns also 1:1 navigation properties:

private static string[] GetNaviProps(Type entityType)//eg typeof(Employee)
{
    return entityType.GetProperties()
                     .Where(p => (typeof(IEnumerable).IsAssignableFrom(p.PropertyType) && p.PropertyType != typeof(string)) ||  p.PropertyType.Namespace == entityType.Namespace)
                     .Select(p => p.Name)
                     .ToArray();
}

Answer 2

I know I'm a little late to the party, but you can use the Entity Framework way to retrieve the navigation properties instead of using reflection:

MetadataWorkspace workspace = ((IObjectContextAdapter)this.Context).ObjectContext.MetadataWorkspace;    
ObjectItemCollection itemCollection = (ObjectItemCollection)(workspace.GetItemCollection(DataSpace.OSpace));   
EntityType entityType = itemCollection.OfType<EntityType>().Single(e => itemCollection.GetClrType(e) == typeof(TEntity));

where this.Context is an instance of the DbContext class. After that you can access the EntityType's NavigationProperties property.