筛选和分页在.NET Core 2.1 EF中不起作用

Question

I try to apply filter and pagination to my GET query. Event when filter and pagination is not null and code reach inside the IF's, query always return all categories. What's the problem?

public async Task<List<Category>> GetListAsync(CategoryListFilter filter = null, Paging paging = null)
{
    var categories = _context.Categories
        .Include(category => category.Image)
        .Include(category => category.Parent)
        .Include(category => category.CategoryProperties)
            .ThenInclude(property => property.Property)
                .ThenInclude(property => property.ValueType)
                    .ThenInclude(valueType => valueType.InputType);

    if (filter != null && !String.IsNullOrEmpty(filter.SearchText))
    {
        categories
            .Where(category => category.Title.Contains(filter.SearchText));
    }

    if(paging != null)
    {
        categories
            .Skip(paging.Offset)
            .Take(paging.Limit);
    }

    return await categories.ToListAsync();
}

Answer 1

You definitely miss

categories = categories
            .Skip(paging.Offset)
            .Take(paging.Limit);

Without it, you call both but discard the result.

The same applies to the Where clause.

(note that this possibly requires providing an explicit type for categories so that both left and right side of the assignment are of the IQueryable<Category> )