InvalidOperationException when fetching joined data with Entity Framework in Blazor Server

I'm working on a Blazor server-side project where I need to fetch and join data from multiple tables using Entity Framework Core in the OnInitializedAsync method. However, I'm encountering the following error:

InvalidOperationException: A second operation was started on this context instance before a previous operation completed. This is usually caused by different threads concurrently using the same instance of DbContext.

Here is my code below:

protected override async Task OnInitializedAsync(){    PeopleTypes = await DbContext.PeopleTypes.Select(pts => new PeopleType        {            Id = pts.Id,            TypeName = pts.TypeName        }).ToListAsync() ?? new List<PeopleType>();    Peoples = await DbContext.People.Select(pl => new People        {            Id = pl.Id,            Name = pl.Name,            CompanyId = pl.CompanyId,            TypeId = pl.TypeId        }).ToListAsync() ?? new List<People>();    CompanyLists = await DbContext.CompanyList.Select(cl => new CompanyList        {            Id = cl.Id,            CompanyName = cl.CompanyName        }).ToListAsync() ?? new List<CompanyList>();    ClassDetails = await DbContext.ClassSessionsDetails    .Where(csd => csd.CsID == CSId)    .Where(csd => csd.CompanyId == selectedCompany)    .Select(csd => new ClassSessionDetails        {            Id = csd.Id,            CsID = csd.CsID        }).ToListAsync();    classMembersData = await DbContext.ClassSessionsDetails        .Join(DbContext.ClassSessionsMembers,            csd => csd.Id,            csm => csm.CSD_Id,            (csd, csm) => new { csd, csm })        .Join(DbContext.People,            combined => combined.csm.PeopleId,            people => people.Id,            (combined, people) => new { combined.csd, combined.csm, people })        .GroupJoin(DbContext.CompanyList,            combined => combined.people.CompanyId,            company => company.Id,            (combined, companies) => new { combined.csd, combined.csm, combined.people, company = companies.FirstOrDefault() })        .GroupJoin(DbContext.PeopleTypes,            combined => combined.people.TypeId,            peopleType => peopleType.Id,            (combined, peopleTypes) => new { combined.csd, combined.csm, combined.people, combined.company, peopleType = peopleTypes.FirstOrDefault() })        .Select(result => new ClassMembers            {                PeopleId = result.people.Id,                Name = result.people.Name,                CompanyId = result.company.Id,                CompanyName = result.company.CompanyName,                PeopleTypeId = result.peopleType.Id,                PeopleTypeName = result.peopleType.TypeName            }).ToListAsync();    await base.OnInitializedAsync();}

Does anyone have suggestions on how to resolve this issue, or how I can improve my query to avoid concurrent operation conflicts? Thank you.