c# Entity Framework - Generics solution

Question

Is there a generics solution for the following code?

public static int SaveReorder(IList<int> listItems)
    {
        int result = 0;
        int order = 1;
        Entity1 db = null;

        using (ObjectContext context = new ObjectContext())
        {
            foreach (int id in listItems)
            {
                db = Get(context, id);
                db.Order = order;
                context.SaveChanges();
                order += 1;
            }
            result = 1;
        }
        return result;
    }

listItems contains an ordered sequence of identitykeys. Entity1 is one of the EntityObjects from our EDM. Get(...) is a custom method in the same class to get an EntityObject on basis of the current ObjectContext and by Id.

We want a generic solution for this implementation so we can apply this for several EntityObjects, where the property 'Order' is a common property for all the EntityObjects. Is this possible?

Yannick Motton · Accepted Answer · 2009-08-29 11:10:21Z

1

Two options come to mind, as Akash has already suggested:

Either let the Entities implement an Interface with an 'Order' Property:

interface IEntityOrder { int Order { get; set; } }

partial class Entity1 : EntityObject { }

partial class Entity1 : IEntityOrder { public int Order { get; set; } }
Or use reflection to set the value of the 'Order' Property (or FieldInfo if it's a field):

PropertyInfo pi = db.GetType().GetProperty("Order");

pi.SetValue(db, newValue, null);

answered Aug 29, 2009 at 11:10

Yannick Motton

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Comments

Akash Kava · Accepted Answer · 2009-08-29 07:56:12Z

1

No, however in future C# 4.0 using dynamic keywords you can do that.

Implementing Interface with Order Property

Currently you can have an interface with order property implemented by each class, I am not sure how to do this in EDM, but it shouldnt be difficult.

We get this kind of problem a lot, thats why C# is coming with dynamic type, we rely on either interfaces or reflection.

answered Aug 29, 2009 at 7:56

Akash Kava

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Comments

Pieter · Accepted Answer · 2009-08-29 12:18:31Z

OK. Thanx all for your answers. Here's my solution.

public static int SaveReorder<T>(IList<int> listItems) where T : EntityObject
    {
        int result = 0;
        int volgorde = 1;
        T entityObject = null;

        using (vgplannewEntities objectContext = new vgplannewEntities())
        {
            try
            {
                foreach (int id in listItems)
                {
                    entityObject = objectContext.GetEntityByKey<T>(id, new String[] { });
                    PropertyInfo pi = entityObject.GetType().GetProperty("Volgorde");
                    pi.SetValue(entityObject, volgorde, null);
                    objectContext.SaveChanges();
                    volgorde += 1;
                }
                result = 1;
            }
            catch
            {
                result = 0;
            }
        }
        return result;
    }

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