c#asp.net-core filter entity-framework-core aspnetboilerplate

How to implement Entity Framework Core data filters?

In my ASP.NET Zero application, I want to setup data filters by CompanyId value. So I read the documents here and the information provided on this support forum thread.

In my EF Core project, I made the following change.

public override void PreInitialize()
{
    if (!SkipDbContextRegistration)
    {
        // ...

        Configuration.UnitOfWork.RegisterFilter("CompanyFilter", false);
    }
}

I then followed the pattern used for IMustHaveTenant data filter and applied the changes below into my DB context class:

protected int? CurrentCompanyId = null;
protected bool IsCompanyFilterEnabled => CurrentCompanyId != null && CurrentUnitOfWorkProvider?.Current?.IsFilterEnabled("CompanyFilter") == true;    

protected override bool ShouldFilterEntity<TEntity>(IMutableEntityType entityType)
{
    if (typeof(IHasCompany).IsAssignableFrom(typeof(TEntity)))
    {
        return true;
    }
    return false;
}

protected override Expression<Func<TEntity, bool>> CreateFilterExpression<TEntity>()
{
    Expression<Func<TEntity, bool>> expression = null;

    if (typeof(IHasCompany).IsAssignableFrom(typeof(TEntity)))
    {
        Expression<Func<TEntity, bool>> companyFilter = e => ((IHasCompany)e).CompanyId == CurrentCompanyId || (((IHasCompany)e).CompanyId == CurrentCompanyId) == IsCompanyFilterEnabled;
        expression = expression == null ? companyFilter : CombineExpressions(expression, companyFilter);
    }
    return base.CreateFilterExpression<TEntity>();
}

Then, in my app service method where I wish to apply the filter, I added the code below.

public async Task<PagedResultDto<EmployeeListDto>> GetEmployees(GetEmployeeInput input)
{
    using (CurrentUnitOfWork.EnableFilter("CompanyFilter"))
    {
        using (CurrentUnitOfWork.SetFilterParameter("CompanyFilter", "CompanyId", GetCurrentUserCompany()))
        {
            // ...
        }
    }
}

In the DB context class, if I hard code a CompanyId value on the line below, the filter works just fine.

protected int? CurrentCompanyId = 123;

I will be honest, I do not fully understand the code that is being used in the CreateFilterExpression method in the DB context class. I borrowed this straight from the ABP GitHub repo code for IMustHaveTenant filter.

I have modified the ABP user "My Settings" modal to include CompanyId. This permits each user to be assigned to a company and thus the application should restrict all data by company for this user.

In my app service base class, I have a method named GetCurrentUserCompany. This method gets the current user's default company. This is the value that should be used on the data filter for company.

Questions:

Do I need to set this company value in the DB context class?
If yes, then how do I call an app service or repository method to get the CompanyId in this DB context class?

Update: I added the code suggested by Aaron and its still not working. I'm testing with a user Id who has company 1 assigned. Yet when the data loads, it still showing them company 1 and 2.

When line 77 executes and does the GetAll call on the repository, its still showing all companies to the user.

Oct 6 Update: The new code works, but only when the user has a company Id assigned. When the user does not have a company assigned, the error shown in the image below is thrown.

Solution

Do I need to set this company value in the Db context class?

If yes, then how do I call an app service or repository method to get the company Id in this DB context class?

No. Implement a getter in your DbContext class:

// using Abp.Collections.Extensions;

// protected int? CurrentCompanyId = null;
protected int? CurrentCompanyId => GetCurrentCompanyIdOrNull();

protected virtual int? GetCurrentCompanyIdOrNull()
{
    if (CurrentUnitOfWorkProvider != null &&
        CurrentUnitOfWorkProvider.Current != null)
    {
        return CurrentUnitOfWorkProvider.Current
            .Filters.FirstOrDefault(f => f.FilterName == "CompanyFilter")?
            .FilterParameters.GetOrDefault("CompanyId") as int?;
    }

    return null;
}

Return expression in your CreateFilterExpression method:

protected override Expression<Func<TEntity, bool>> CreateFilterExpression<TEntity>()
{
    // Expression<Func<TEntity, bool>> expression = null;
    var expression = base.CreateFilterExpression<TEntity>();

    if (typeof(IHasCompany).IsAssignableFrom(typeof(TEntity)))
    {
        Expression<Func<TEntity, bool>> companyFilter = e => ((IHasCompany)e).CompanyId == CurrentCompanyId || (((IHasCompany)e).CompanyId == CurrentCompanyId) == IsCompanyFilterEnabled;
        expression = expression == null ? companyFilter : CombineExpressions(expression, companyFilter);
    }

    // return base.CreateFilterExpression<TEntity>();
    return expression;
}