Try this:
cmbEntity.DataSource =
store.Entities
.ToList()
.Select(e => new {Id = e.Id, Name = e.Id + e.Name});
or you can use
cmbEntity.DataSource =
store.Entities
.Select(e => new {Id = e.Id,
Name = SqlFunctions.StringConvert((decimal)e.Id + e.Name});
In this case you must add reference to assembly System.Data.Entity.dll
and import namespace System.Data.Objects.SqlClient
.