Question

I come from a PHP/MySQL background, so maybe the problems I’m having with .NET stem from that. After a week of posting how to create an inventory tracker for our computer hardware and software, someone finally told me that he thought I was doing things wrong. The issue was not my code, but my design. That’s certainly possible. I’m trying to do this in EF Code First and the idea of generating a database with code is foreign to me. However, I got the database working and everything was pointing to the right thing. But I can’t pull what I need from the database.

What I want to do is create a dashboard page that would have categories for the types of hardware. So there would be a list of PCs, a list of monitors, a list of printers, etc. Initially, what I did was based on my knowledge of MySQL. I created a Hardware table (class) and a HardwareTypes table (class). In MySQL, what I would have done is put the ID for the HardwareType in the Hardware table, so I could do joins. Then I can get all of my PCs with a simple inner join.

.NET seems like it’s different. It wants to create an intermediate table — HardwareHardwareTypes, and then connect the two other tables. That seems strange, but OK. But when I go to get all of my PCs, I can’t seem to get the help I need to write the query. So please take a look at my query and my classes, and let me know your thoughts.

Query, which returns Hardware, not HardwareTypes — how do I get HardwareTypes?):

var pcs = db.Hardware.Where(h => h.HardwareType.Any(hwt => hwt.HType == "PC"));
ViewBag.Pcs = pcs.ToList();

Hardware class:

public class Hardware
    {
        public int Id { get; set; }
        public virtual ICollection<DeviceType> Type { get; set; }
        public string AssetTagId { get; set; }
        public virtual ICollection<Manufacturer> Manufacturer { get; set; }
        [Required]
        [StringLength(50)]
        public string ServiceTagId { get; set; }
        [Required]
        [StringLength(50)]
        public string SerialNumber { get; set; }
        [Required]
        [StringLength(75)]
        public string ProductNumber { get; set; }
       // [Required]
        [StringLength(20)]
        public string PurchaseDate { get; set; }
        [StringLength(20)]
        public string WarrantyExpiration { get; set; }
        [Required]
        [StringLength(20)]
        public string WarrantyType { get; set; }
        public virtual ICollection<Location> Location { get; set; }
        public virtual ICollection<HardwareType> HardwareType { get; set; }
        [Required]
        [StringLength(2000)]
        public string Notes { get; set; }
        public string POATag { get; set; }
    }

HardwareTypes class:

public class HardwareType
    {
        public int Id { get; set; }
        [Required]
        [StringLength(128)]
        public string HType { get; set; }
        public virtual ICollection<Hardware> Hardware { get; set; }
    }

Again, if what I need is more of a high-level design change, please let me know. If I need a different query, let me know that. The third (intermediate) table is dynamically generated and it’s hard to know how to post that. I’d appreciate any and all help with this. What I need in the end is a list of PCs. Here is some sample seed data:

    ... new Hardware { AssetTagId = "2134", 
Type = device.Where(h => h.DType == "Network Device").ToArray(), 
Manufacturer = manuf.Where(h => h.ManufacturerName == "SonicWall").ToArray(), 
ServiceTagId = "5243", 
SerialNumber = "3456", 
ProductNumber = "2345", 
PurchaseDate = "2012-10-23", 
WarrantyExpiration = "2012-11-12", 
WarrantyType = "NBD", 
Location = loc.Where(h => h.LocationName == "Paradise Lane").ToArray(), 
Notes = "Scrapped",  
HardwareType = htype.Where(h => h.HType == "PC").ToArray()}, ...

 var htype = new List<HardwareType> {
                new HardwareType { HType = "PC" },
                new HardwareType { HType = "Monitor" },
                new HardwareType { HType = "Printer" },
                new HardwareType { HType = "Miscellaneous" }
            };

If my seed data is structured wrong, please let me know that. Thanks.

Answer 1

Let me tell you first of all that the same database design which works in PHP/MySQL can work here also.

The easiest approach I will suggest to you is to create a view in the database which joins table Hardware and HardwareType, add nwly created view to you database model and fetch the desired data from the view instead of tables.