Add filter to all query entity framework

Question

I want add CompanyID filter to my all entity framework request.Because each user must see just their records.I dont want add filter (x=>x.CompanyID == cID) all methods in business layer.How can i add automaticly filter to requests.

My GetList method in DAL

     public List<TEntity> GetList(Expression<Func<TEntity, bool>> filter)
    {
        using (var context = new TContext())
        {

            return filter == null
                ? context.Set<TEntity>().ToList()
                : context.Set<TEntity>().Where(filter).ToList();
        }
    }

Business

   public List<FinanceData> GetAll()
        {
            return _financeDal.GetList(filter:x=>x.CompanyID==_cID);
        }

Answer 1

everything you suggest does not work for the following scenario: HasQueryFilter power, but per each HTTP request. ApplyGlobalFilters / OnModelCreating applied once for model creation. But if you reload the page with different request parameters - they won't be taken into account to filter out DbSet. If you add the filter to GetAll call - another call 'Include'-ing the entity won't have this filter. We need real global mechanism to filter out DbSets by specific condition - which may change per each request (page refresh).

Answer 2

In the Entity Framework Core 2.0, you can use Global Query Filters.

1. Add filter just to the one entity:

   public interface IDelete
   {
       bool IsDeleted { get; set; }
   }
   
   public class Blog : IDelete
   {        
       public int BlogId { get; set; }
       public string Name { get; set; }
       public string Url { get; set; }
   
       public List<Post> Posts { get; set; }
   }
   
   public class Post : IDelete
   {
       public int PostId { get; set; }
       public string Title { get; set; }
       public string Content { get; set; }
       public bool IsDeleted { get; set; }
   
       public int BlogId { get; set; }
       public Blog Blog { get; set; }
   }
   
   // Default method inside the DbContext or your default Context
   protected override void OnModelCreating(ModelBuilder modelBuilder)
   {         
       base.OnModelCreating(builder);  
   
       modelBuilder.Entity<Blog>()
                   // Add Global filter to the Blog entity
                   .HasQueryFilter(p => p.IsDeleted == false);
   
       modelBuilder.Entity<Post>()
                   // Add Global filter to the Post entity
                   .HasQueryFilter(p => p.IsDeleted == false);
   }
   

2. If you have many entities, the first way isn't good, Use below code for applying the global filter to all entities(Magic way):

   public static class ModelBuilderExtension
   {
       public static void ApplyGlobalFilters<TInterface>(this ModelBuilder modelBuilder, Expression<Func<TInterface, bool>> expression)
       {
           var entities = modelBuilder.Model
               .GetEntityTypes()
               .Where(e => e.ClrType.GetInterface(typeof(TInterface).Name) != null)
               .Select(e => e.ClrType);
           foreach (var entity in entities)
           {
               var newParam = Expression.Parameter(entity);
               var newbody = ReplacingExpressionVisitor.Replace(expression.Parameters.Single(), newParam, expression.Body);    
               modelBuilder.Entity(entity).HasQueryFilter(Expression.Lambda(newbody, newParam));
           }
       }
   }
   
   // Default method inside the DbContext or your default Context
   protected override void OnModelCreating(ModelBuilder builder)
   {
       base.OnModelCreating(builder);
   
       modelBuilder.Entity<Blog>();
       modelBuilder.Entity<Post>();
   
       builder.ApplyGlobalFilters<IDelete>(e => e.IsDeleted == false);
   }
   

And Queries will be:

    exec sp_executesql N'SELECT [x].[BlogId], [x].[Name], [x].[Url]
    FROM [dbo].[Blog] AS [x]
    WHERE [x].[IsDeleted] = 0'

Answer 3

You can also extend the object context and add an extension method that returns IQueryable

Like

public class CustomdbContext : DbContext
{       
    public IQueryable<TEntity> ApplyCustomerFilter<TEntity>(IQueryable<TEntity> query) where TEntity : Customer 
    {
         return query.Where(x => x.CustomerId == customerctxId);
    }
}

Answer 4

You can implement IHasCompanyId interface in such entities. And then implement repository pattern as:

public class MyRepository<T>
{
    public MyRepository(DbContext dbContext, int companyID)
    {
        if (dbContext == null) 
            throw new ArgumentNullException("Null DbContext");
        DbContext = dbContext;
        DbSet = DbContext.Set<T>();

        CompanyID = companyID;
    }

    protected DbContext DbContext { get; set; }
    protected int CompanyID  { get; set; }

    protected DbSet<T> DbSet { get; set; }

    // Add filter here
    public virtual IQueryable<T> GetAll()
    {
        if(typeof(IHasCompanyID).IsAssignableFrom(typeof(T)))
            return DbSet.Where(x => x.CompanyID == CompanyID);
        else 
            return DbSet;
    }
}

And initialize _financeDal as:

var _financeDal = new MyRepository<TEntity>(dbContext, companyID);