CODEWITHSUNDEEP
c#reflectioncastingentity-framework-6
Kyle
Kyle

Reputation: 1011

How to cast DbSet<T> to List<T>

Given the following simplified Entity Framework 6 context, I am trying to populate a List with the entities but having problems with how to cast (I believe) via reflection.

public class FooContext : DbContext
{
   public virtual IDbSet<FooClass> Foo { get; set; }    
   //...
}

public class FooClass
{
    public int Id{ get; set; }
    public string Name {get; set; }
    //...    
}

public main()
{
     using (var context = new FooContext())
     {
         var sets = typeof(FooContext).GetProperties().Where(pi => pi.PropertyType.IsInterface && pi.PropertyType.GetGenericTypeDefinition().ToString().ToLower().Contains("idbset"));

         foreach (var set in sets)
         {
             //When I debug and enumerate over 'value' the entire results are shown so I believe the reflection part is OK.
             var value = set.GetValue(context, null);

             //Always returns null. How can I cast DbSet<T> to List<object> or List<T>? 
             var list = value as List<object>();

             //...
         }
     }
}

I'm doing this for utility method for some integration testing I am doing. I am trying to do this without using direct inline SQL calls (using SqlConnection and SqlCommand etc) to access the database (as the datastore may change to Oracle etc).

Upvotes: 15

Views: 47564

Answers (4)

AzzamAziz
AzzamAziz

Reputation: 2161

Alongside VicYam's answer, here is an easier way with a detailed explanation.

Once you add the System.Linq namespace, you no longer need to get IQueryable and then convert to a List. Instead, you will get the extension methods on the DbSet object.

What does this mean? You can simply return the DbSet by itself as it inherits from IEnumerable. The consumer, possibly a dev, can then do a .ToList or any other list type they may need.

Easiest

This will return the DbSet as is, which already inherits from IEnumerable which is a list type that can be then converted to a List.

List<ObjectType> list = new List<ObjectType>();
using (var context = new FooContext())
{
    list = context.Foo;
}

Alternative

You can immediately convert from IEnumerable to a List.

using (var context = new FooContext())
{
    var list = context.Foo.ToList();
}

Still want VicYam's answer but as a one line?

using (var context = new FooContext())
{
    var list = context.Foo.AsQueryable().ToList();
}

Upvotes: 7

VicYam
VicYam

Reputation: 111

//dont forget using System.Linq;
using (var context = new FooContext())
{
   IQueryable<FooClass> rtn = from temp  in context.Foo select temp;
   var list = rtn.ToList();
}

Upvotes: 11

Siddarth Kanted
Siddarth Kanted

Reputation: 5906

private StudentDatabaseEntities db = new StudentDatabaseEntities();

public List<StudentDatabaseDbTableModel> AllProducts()
{
    return db.StudentDatabaseDbTableModel.ToList();
}

db.StudentDatabaseDbTableModel is of type DbSet. ToList is a method inside DbSet class. ToList method converts object of type DbSet to List type.

Upvotes: -1

LInsoDeTeh
LInsoDeTeh

Reputation: 1038

IDBSet inherits from IQueryable<TEntity>, IEnumerable<TEntity>, IQueryable, and IEnumerable, so you can't directly cast it to a list that way. You could get a List<TEntity> of all entities in the DBSet though by using .ToList() or .ToListAsync()

THis creates a copy of all entities in memory though, so you should consider operating with LINQ directly on the DBSet

Upvotes: 13

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