Is it possible to implement a extension method to ObjectContext Class which filters the database rows and returns the ObjectSet<TEntity>

Question

Hi,

     Please refer to the following link 

http://social.msdn.microsoft.com/Forums/en-US/adodotnetentityframework/thread/9ae8d33b-2684-46cd-a77f-ed4a6432cce0

This question is related to the above link. I m trying different approach for the issue mentioned in the link. I will explain the idea i have in my mind. I m planning to write a extension method to ObjectContext class which is similar to overloaded methods it has

1.public ObjectSet<TEntity> CreateObjectSet<TEntity>() where TEntity : class

2.public ObjectSet<TEntity> CreateObjectSet<TEntity>(string entitySetName) where TEntity : class

Which returns the rows from database of type ObjectSet<TEntity>. If you want filter we can add where class to it which returns ObjectQuery<TEntity>. The Extension method filters the rows and returns them as ObjectSet<TEntity>

Extension Method - 

public static ObjectSet<TEntity> CreateFilteredObjectSets<TEntity>(this ObjectContext context, string entitySetName) where TEntity : class
        {

//Actually ObjectSet already has method Where()

//Which it inherits from ObjectQuery, so its return type is ObjectQuery<TEntity>

//But What I m looking for where method which filters objects and returns objects of type ObjectSet<TEntity> instead of ObjectQuery<TEntity>

return base.CreateObjectSet<TEntity>("EntityName").Where(condition);

}

Extension method above is Psuedocode I have in my mind. Let me know this is possible first. If so how to implement this??

Thanks

Murali

Answer 1

OR

Can I write a Extension method where() which returns ObjectSet<TEntity> to the ObjectSet Class??

Answer 2

Where statement will always return a ObjectQuery<T> type or a IQueryable<T> type, so a method return a filterd ObjectSet is not possible.

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Go go Doraemon!

Answer 3

Ok I will put my question in different way. Extension method which filters the entity rows and returns ObjectSet<TEntity>

public static ObjectSet<TEntity> CreateFilteredObjectSets<TEntity>(this ObjectContext context, string entitySetName) where TEntity : class
        {

//Actually ObjectSet already has method Where()

//Which it inherits from ObjectQuery, so its return type is ObjectQuery<TEntity>

//But What I m looking for is method which filters objects and returns objects of type ObjectSet<TEntity> instead of ObjectQuery<TEntity>

}

I am not talking about the Where method here. Just some extension method which could solve the above issue using the some other API's exposed by Entity Framework.

Answer 4

Not possible, if you do a filter, the return type will never be ObjectSet type. If you could clarify what the apis you want to use only exposed for ObjectSet, maybe I can help you to think if there's another way.

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Go go Doraemon!

Answer 5

Hi SmaaartCoder,

I agree with @Dorado999, if you do a filter in the method, the return type will not be ObjectSet.

Best Regards

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Allen Li [MSFT]
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