Question

I am trying to build a controller that services edit requests for all my lookup tables. I have several DbSet variables on my DbContext that derive from IdNamePairBase, e.g:

public DbSet<Country> Countries { get; set; } // Country derives from IdNamePairBase

How can I pass the name of one of these to a query, to get all items in that list? E.g.

var list = db.GetNamedDbSet("Countries");

Then, for bonus points I need to get an IEnumerable<IdNamePairBase> from list.

Answer 1

You could use the Set(Type type) on the DbContext if the name of the table corresponds to the type.

 public IEnumerable<IdNamePairBase> GetNamedDbSet(string dbSetName)
 {
      var property = Type.GetType(dbSetName);
      if (property == null || !property.CanRead)
      {
         throw new ArgumentException("DbSet named " + dbSetName + " does not exist." );
      }

      // at this point you might want to check that the property is an enumerable type
      // and that the generic definition is convertible to IdNamePairBase by
      // inspecting the property type.  If you're sure that these hold, you could
      // omit the check.

      return Set(type).Cast<IdNamePairBase>();
 }

Original Answer

If the name of the set matches the property name, you can use reflection.

 public IEnumerable<IdNamePairBase> GetNamedDbSet( string dbSetName )
 {
      var property = this.GetType().GetProperty( dbSetName );
      if (property == null || !property.CanRead)
      {
         throw new ArgumentException("DbSet named " + dbSetName + " does not exist." );
      }

      // at this point you might want to check that the property is an enumerable type
      // and that the generic definition is convertible to IdNamePairBase by
      // inspecting the property type.  If you're sure that these hold, you could
      // omit the check.

      var result = new List<IdNamePairBase>();
      foreach (var item in (IEnumerable)property.GetValue( this, null))
      {
          result.Add( (IdNamePairBase)item );
      }
      return result;
 }