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Entity Framework Classic Query Filter

Description

The Query Filter feature allows you to filter returned entities from a query using a predicate (where clause).

public class EntityContext : DbContext
{
	public EntityContext() : base(FiddleHelper.GetConnectionStringSqlServer())
	{
		// Add your Global Query Filter here
		this.Configuration.QueryFilter.Filter<ISoftDelete>(customer => !customer.IsDeleted);
	}
	
	public DbSet<Customer> Customers { get; set; }
}

// SELECT * FROM Customers WHERE IsDeleted = 0
var list = context.Customers.ToList();

Try it: NET Core | NET Framework

The filter is applied in the database and application side:

  • Database side: Whenever possible, the filter is applied in the SQL query.
  • Application side: The filter is always applied to the query result.

This feature allows to exclude or include specific entities to handle scenarios such as:

What is supported?

All cases are supported:

  • Include
  • Lazy Loading
  • Many to Many
  • Etc.

Advantage

  • Centralize logic in Query Filter instead of adding it on every queries
  • Reduce the chance of missing a filter when creating a new query
  • Improve code readability
  • Improve development productivity

Getting Started

Global Query Filter

You can create a Global Query Filter inside your context constructor. This filter will be used by all your context instances.

public class EntityContext : DbContext
{
	public EntityContext() : base(FiddleHelper.GetConnectionStringSqlServer())
	{
		// Add your Global Query Filter here
		this.Configuration.QueryFilter.Filter<ISoftDelete>(customer => !customer.IsDeleted);
	}
	
	public DbSet<Customer> Customers { get; set; }
}

// SELECT * FROM Customers WHERE IsDeleted = 0
var list = context.Customers.ToList();

Try it: NET Core | NET Framework

Instance Query Filter

You can create an Instance Query Filter after a context instance has been created. This filter will be specific to this context instance. If your context instance already has query filter both filters will be enabled.

using (var context = new EntityContext())
{
	// Add your Instance Query Filter here
	context.Configuration.QueryFilter.Filter<ISoftDelete>(customer => !customer.IsDeleted);
	
	// SELECT * FROM Customers WHERE IsActive = 1
	var list = context.Customers.ToList();
	
	FiddleHelper.WriteTable("Customers", list);			
}

Try it: NET Core | NET Framework

Enable/Disable Query Filter

You can enable/disable your Query Filter with the Enable(), Disable(), EnableFilter(id), and DisableFilder(id) methods.

using (var context = new EntityContext())
{
	var filter = context.Configuration.QueryFilter.Filter<ISoftDelete>(QueryFilterType.SoftDelete.ToString(), customer => !customer.IsDeleted);
	
	// QueryFilter.Disable()
	{
		filter.Disable();

		// SELECT * FROM Customers
		var list = context.Customers.ToList();

		FiddleHelper.WriteTable("Customers", list);
	}

	// QueryFilter.Enable()
	{
		filter.Enable();

		// SELECT * FROM Customers WHERE IsActive = 1
		var list = context.Customers.ToList();

		FiddleHelper.WriteTable("Customers", list);
	}
	
	// QueryFilterManager.DisableFilter(string id)
	{
		// DOC: You can enable/disable your `QueryFilter` with the `Enable()`, `Disable()`, `EnableFilter(id)`, and `DisableFilder(id)` methods.
		context.Configuration.QueryFilter.DisableFilter(QueryFilterType.SoftDelete.ToString());

		// SELECT * FROM Customers
		var list = context.Customers.ToList();

		FiddleHelper.WriteTable("Customers", list);
	}

	// QueryFilterManager.EnableFilter(string id)
	{
		// DOC: You can enable/disable your `QueryFilter` with the `Enable()`, `Disable()`, `EnableFilter(id)`, and `DisableFilder(id)` methods.
		context.Configuration.QueryFilter.EnableFilter(QueryFilterType.SoftDelete.ToString());

		// SELECT * FROM Customers WHERE IsActive = 1
		var list = context.Customers.ToList();

		FiddleHelper.WriteTable("Customers", list);
	}
}

Try it: NET Core | NET Framework

DANGER:

DO NOT disable Global Query Filter unless you want to disable the filter for all your context instances.

HINT:

Use an enum when using a specified ID QueryFilterType.FilterName.ToString() to avoid hardcoding a string.

Real Life Scenarios

Soft Delete

Your application uses Soft Delete/Logical Delete to delete entities.

The Query Filter allows you to exclude all entities that are soft deleted from all your queries.

public class EntityContext : DbContext
{
	public EntityContext() : base(FiddleHelper.GetConnectionStringSqlServer())
	{
		// Add your Global Query Filter here
		this.Configuration.QueryFilter.Filter<ISoftDelete>(customer => !customer.IsDeleted);
	}
	
	public DbSet<Customer> Customers { get; set; }
}

// SELECT * FROM Customers WHERE IsDeleted = 0
var list = context.Customers.ToList();

Try it: NET Core | NET Framework

HINT:

The filter is usually applied to an interface named ISoftDelete inherited by all entity types that use Soft Delete.

Multi-Tenancy

Your application uses a single instance to serve multiple tenants.

The Query Filter allows you to include only data that is related to the specified TenantID to all your queries.

public static int ApplicationTenantID = 1;

public class EntityContext : DbContext
{
	public EntityContext() : base(FiddleHelper.GetConnectionStringSqlServer())
	{
		// Add your Global Query Filter here
		this.Configuration.QueryFilter.Filter<ITenant>(x => x.TenantID == ApplicationTenantID);
	}
	
	public DbSet<Customer> Customers { get; set; }
}

// SELECT * FROM Customers WHERE TenantID = 1
var list = context.Customers.ToList();

Try it: NET Core | NET Framework

HINT:

The filter is usually applied to an interface named ITenant inherited by all entity types that use multi-tenancy.

Logical Data Partitioning

Your application stores data in the same table but only a specific range should be available by example for a country.

The Query Filter allows you to include only data available for the specified country to all your queries.

// TODO
// [Try it](8c3zgI)

Security Access

Your application has security access. The logged user can only view some data depending on his role.

The Query Filter allows you to include only data the user has access to all your queries.

public static int CurrentRoleId = 1; // admin

public class EntityContext : DbContext
{
	public EntityContext() : base(FiddleHelper.GetConnectionStringSqlServer())
	{
		this.Configuration.QueryFilter.Filter<ISoftDelete>(customer => !customer.IsDeleted || CurrentRoleId == 1);
		this.Configuration.QueryFilter.Filter<Customer>(customer => customer.Type == CustomerType.Web || CurrentRoleId == 1);
	}
	
	public DbSet<Customer> Customers { get; set; }
}

Try it: NET Core | NET Framework

Documentation

QueryFilter

Properties
Name Description Example
ID Gets the QueryFilter ID. NET Core / NET Framework
EntityType Gets the QueryFilter entity type on which the filter is applied. NET Core / NET Framework
IsEnabled Gets if the QueryFilter is enabled. Use Enable() and Disable() method to change the state. Always return false if the QueryFilter feature is disabled. NET Core / NET Framework
Methods
Name Description Example
Enable() Enable the QueryFilter. NET Core / NET Framework
Disable() Disable the QueryFilter. NET Core / NET Framework

QueryFilterManager

Properties
Name Description Example
IsEnabled Gets or sets if the QueryFilter feature is enabled. NET Core / NET Framework
Methods
Name Description Example
Filter<T>(Expression<Func<T, bool>> filter) Filter an entity type using a predicate. NET Core / NET Framework
Filter<T>(string id, Expression<Func<T, bool>> filter) Filter an entity type using a predicate. The QueryFilter will be created with the specified ID. NET Core / NET Framework
EnableFilter(string id) Enable the QueryFilter with the specified id. NET Core / NET Framework
DisableFilter(string id) Disable the QueryFilter with the specified id. NET Core / NET Framework
GetFilter(string id) Get the QueryFilter with the specified id. NET Core / NET Framework

Limitations

Change Tracker

If an entity is already loaded in the ChangeTracker, the filter may not apply due to how the ChangeTracker works.

For example:

  1. You load a customer with all his invoices
  2. You add a filter to the invoice entity type
  3. You load the same customer with all his invoices
  4. The customer invoices have not been filtered

T