I can't wrap my mind around this issue and haven't found the correct search keys yet:
I would like to have several categories of items in which all items have specific attributes. Those attributes (text fields, dropdowns, or checkboxes) should be added to a category and I want to edit and save those attributes for each item.
I'm working with MVC 4 and code-first EF5. How can I implement this?
My first approach were several classes like Text, Dropdown that were inherited from an abstract Attribute class and a Category class like this:
public class Category
{
[Key]
public int CategoryId { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public virtual ICollection<Item> Items { get; set; }
public virtual ICollection<Attribute> Attributes { get; set; }
}
But then I had no idea to proceed. Am I on the right way or completely wrong? Can someone give me a few hints I can search for?
Edit
Ultimately I'm trying to build a list of hifi devices. Speakers have different attributes than amplifier and those have different attributes to tape recorders. I would like to give a unified look for the details of each device and pre-define specific attributes to that category with an additional free-for-all text area. Speaker XYZ is my item, Speaker my category and dB an attribute.
Ok so this question is basically about the data design.
First, I assume that the rule is:
One item has one category
One category has many attributes
One item has many attributes associated with the category
For rule no.1, it is good enough in your design. (simplified example)
public class Category{
public IEnumerable<Item> Items{get;set;}
}
public class Item{
public Category Category{get;set;}
}
Its clear enough.
For rule no.2, I think you should make a CategoryAttribute class. It holds the relation between one to many Category and Attribute. Basically, CategoryAttribute is a master, whereas the children will be ItemAttribute.
public class Category{
public IEnumerable<CategoryAttribute> CategoryAttributes{get;set;}
}
public class CategoryAttribute{
public Category Category{get;set;}
public string CategoryName{get;set;}
public string DefaultValue{get;set;} // maybe a default value for specific
// attribute, but it's up to you
public IEnumerable<ItemAttribute> ItemAttributes{get;set;}
}
The IEnumerable<ItemAttribute> is the one to many relation between category attribute and item attribute.
For rule no.3, the the ItemAttribute described in rule no.2 will be represented attribute owned by each item.
public class Item{
public IEnumerable<ItemAttribute> ItemAttributes{get;set;}
}
public class ItemAttribute{
public Item Item {get;set;} // it owned by one attribute
public CategoryAttribute{get;set;} // it owned by one category attribute
}
I don't quite sure about how to represent relation or primary and foreign key in code first. Hopefully I can enhance my answer if needed (and if I able). But hopefully my illustration about relations and the class designs for each objects.
I think something like this may work for you...
public class Category
{
public int CategoryId { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public virtual ICollection<Item> Items { get; set; }
public virtual ICollection<Attribute> Attributes { get; set; }
}
public class Item
{
public int ItemId { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public int CategoryId { get; set; }
public Category Category { get; set; }
public virtual ICollection<ItemAttribute> ItemAttributes { get; set; }
}
public class Attribute
{
public int AttributeId { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public virtual ICollection<Category> Categories { get; set; }
public virtual ICollection<ItemAttribute> ItemAttributes { get; set; }
}
public class ItemAttribute
{
public int ItemId { get; set; }
public int AttributeId { get; set; }
public Item Item { get; set; }
public Attribute Attribute { get; set; }
public string Value { get; set; }
public int ValueInt{ get; set; }
// etc.
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<ItemAttribute>()
.HasKey(x => new { x.ItemId, x.AttributeId });
modelBuilder.Entity<ItemAttribute>()
.HasRequired(x => x.Item)
.WithMany(x => x.ItemAttributes)
.HasForeignKey(x => x.ItemId)
.WillCascadeOnDelete(false);
modelBuilder.Entity<ItemAttribute>()
.HasRequired(x => x.Attribute)
.WithMany(x => x.ItemAttributes)
.HasForeignKey(x => x.AttributeId)
.WillCascadeOnDelete(false);
// AttributeCategories is created for you - but you can do the same as ^ above to customize
// just change 'ICollection<Category> Categories' to collection of 'ItemAttribute'
}
// use it like e.g.
var item = new Item { Name = "ItemTest", };
var attribute = new Attribute { Name = "attributeTest", };
item.ItemAttributes = new List<ItemAttribute>
{
new ItemAttribute { Item = item, Attribute = attribute, Value = "test", },
};
var category = new Category
{
Name = "cat1",
Items = new[]
{
item,
new Item{ Name = "Item1", },
new Item{ Name = "Item2", },
new Item{ Name = "Item3", },
new Item{ Name = "Item4", },
new Item{ Name = "Item5", },
},
Attributes = new[]
{
attribute,
new Attribute{ Name = "att1", },
new Attribute{ Name = "att2", },
}
};
db.Categories.Add(category);
db.SaveChanges();
var categories = db.Categories.ToList();
ItemAttribute is used to connect and store values.
And you're going to need to further adjust as per your requirements.
I actually never worked with code first approach, but I can give you some idea about how this scenario can be handled...To me, it looks that Item is the major one instead of Category. So you can have this structure...
public class Category
{
[Key]
public int CategoryId { get; set; }
public string CategoryName { get; set; }
public string CategoryDescription { get; set; }
// use attributes here if you want them for Category
//public Dictionary<string, string> ItemnAttributes { get; set; }
}
public class MyItem
{
[Key]
public int ItemId { get; set; }
public string ItemName { get; set; }
public string ItemDescription { get; set; }
public Category ItemnCatagory { get; set; }
public Dictionary<string, string> ItemnAttributes { get; set; }
}
Hope this helps..
Related
IQueryable<Product> product = objContext.Set<Product>().Include(p =>
p.Categories.Name).Where(p => p.Id == 2);
As per the current view, I'm getting an error. It says add other model with their properties. i.e. to include Category model and corresponding Name property.
#model IEnumerable<>crudOneToMany.Models.Product>
using viewmodel, is it possible to join two tables?
View
Error
A specified Include path is not valid. The EntityType 'crudOneToMany.Models.Category' does not declare a navigation property with the name 'Name'.
public class Product
{
public int Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public int CategoryId { get; set; }
public virtual Category Categories { get; set; }
}
public class Category
{
public int Id { get; set; }
public string Name { get; set; }
public ICollection<Product> Products { get; set; }
}
public class ProductDBContext : DbContext
{
public ProductDBContext()
: base("ProductDBContext")
{
}
public DbSet<Product> Products { get; set; }
public DbSet<Category> Categories { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Product>().HasRequired(o => o.Categories).WithMany(o => o.Products).HasForeignKey(o => o.CategoryId);
base.OnModelCreating(modelBuilder);
}
}
Your problem is here:
.Include(p => p.Categories.Name)
Instead you should write .Include(p => p.Categories)
This means that in output there will be loaded Categories navigation collection to product.
Name is simple string property (is not navigation property so it should not be included)
Here is the proposed ViewModel for you.
ProductViewModel.cs
public class ProductViewModel
{
public int Id { get; set; }
[Required(ErrorMessage = "required")]
public string ProductName { get; set; }
public Category Category { get; set; }
public ICollection<Category> Categories { get; set; }
}
I am trying to create a view (with Razor engine) by mapping the model class to Person class through the Add View option in Visual Studio 2013.
When it creates a view it only creates Age, Gender, Name fields. However, I need a view which would list down all the properties in each class; i.e. I need a view which contains the following fields: Age, Name, Gender, EmployerName, Salary, City, State, and Country.
I have a a class similar to this:
public class Person
{
public int Age { get; set }
public string Gender { get; set; }
public string Name { get; set; }
public JobDetails JobDetailsInfo { get; set; }
public Address AddressInfo { get; set; }
}
public class JobDetails
{
public string EmployerName { get; set; }
public string Designation { get; set; }
public int Salary { get; set; }
}
public class Address
{
public string City { get; set; }
public string State { get; set; }
public int Country { get; set; }
}
As your relationships are 1:1, this is pretty straight-forward.
You'll have to manually edit the view. Assuming the Model is of type Person, here's an example row:
<tr>
<td>#Model.Age</td>
<td>#Model.Name</td>
<td>#Model.Gender</td>
<td>#Model.JobDetailsInfo.EmployerName</td>
<td>#Model.JobDetailsInfo.Salary</td>
<td>#Model.AddressInfo.City</td>
<td>#Model.AddressInfo.State</td>
<td>#Model.AddressInfo.Country</td>
</tr>
This will work as long as you have that simple relationship, but if what you've shown does not correctly represent any normalisation you've applied to the data structure, this will fall flat on its face.
create the view manually or use inheritence...something like
public class jobdetails : person
{
}
I slightly changed my class structure and i created partial views for commondata,jobdetails and address and used them in my main view using #Html.Partial. I was able to pass default data by creating an object instance and loading some default values and passed the entire object to the view .The catch here is the model class which is bind to the Parent view must conatin all properties which are used for creating partial views. Pls see below
Controller method:
//Assign all properties for person object here
return View("ViewName", "PersonObject");
.cshtml:
#Html.Partial("ViewPath",Model.Data)
#Html.Partial("ViewPath",Model.JobDetailsInfo )
#Html.Partial("ViewPath",Model.AddressInfo )
public class Person
{
public CommonData Data
public JobDetails JobDetailsInfo { get; set; }
public Address AddressInfo { get; set; }
}
public class CommonData
{
public int Age { get; set }
public string Gender { get; set; }
public string Name { get; set; }
}
public class JobDetails
{
public string EmployerName { get; set; }
public string Designation { get; set; }
public int Salary { get; set; }
}
public class Address
{
public string City { get; set; }
public string State { get; set; }
public int Country { get; set; }
}
I have those 2 Models
public class BranchEmployees
{
public int ID { get; set; }
[Required, Column(Order = 0), Key]
public string ApplicationUserID { get; set; }
[Required, Column(Order = 1), Key]
public int BranchID { get; set; }
public virtual ICollection<ApplicationUser> ApplicationUser { get; set; }
public virtual ICollection<Branch> Branch { get; set; }
}
public class Branch
{
public int ID { get; set; }
public string BranchName { get; set; }
[Required]
public string ApplicationUserID { get; set; }
public ApplicationUser User { get; set; }
public virtual ICollection<BranchEmployees> BranchEmployees { get; set; }
}
public class ApplicationUser
{
//rest of the code
}
UPDATE
I have everything set up but what I want is the query that gets me the Employees whose IDs are in the branch employees table
, I'm using entity framework code first with MVC 5 , how do I do it ?
Assuming that your ApplicationUser class will have a navigational property called BranchEmployees, here is the query that gets me the Employees whose IDs are in the branch employees table
List<ApplicationUsers> employeeNames =
dbContext
.ApplicationUsers
.Where(au => au.BranchEmployees
.Count() > 0).ToList();
Also, can you provide whole model including ApplicationUser? I also wonder why you do not prefer BranchEmployees to inherit from ApplicationUser.
You don't need a class that indicates a many-to-many relation between two tables when you do code-first. The key here is to create virtual properties of those classes. Lets say you have a class Student and class Course. Students can be in many Courses and Courses can have many Students. To generate a database using these models the classes should look like this:
public class Student
{
private ICollection<Course> _courses;
public Student()
{
this._courses = new HashSet<Course>();
}
[Key]
public int Id { get; set; }
public string FullName { get; set; }
public virtual ICollection<Course> Courses
{
get { return this._courses; }
set { this._courses = value; }
}
}
And for Course:
public class Course
{
private ICollection<Student> _students;
public Course()
{
this._students = new HashSet<Student>();
}
[Key]
public int Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public virtual ICollection<Student> Students
{
get { return this._students; }
set { this._students = value; }
}
}
I hope that this can help you solve your issue.
I'm using ASP.NET MVC4 EF CodeFirst.
Need help to write LINQ (to entities) code in Index action to get collection of Courses which are attended by selected student. The relationship is many to many with join table with payload.
//StudentController
//-----------------------
public ActionResult Index(int? id)
{
var viewModel = new StudentIndexViewModel();
viewModel.Students = db.Students;
if (id != null)
{
ViewBag.StudentId = id.Value;
// *************PROBLEM IN LINE DOWN. HOW TO MAKE COURSES COLLECTION?
viewModel.Courses = db.Courses
.Include(i => i.StudentsToCourses.Where(t => t.ObjStudent.FkStudentId == id.Value));
}
return View(viewModel);
}
The error I got is:
The Include path expression must refer to a navigation property defined on the type. Use dotted paths for reference navigation properties and the Select operator for collection navigation properties.
I have modeles (the third one is for join table with payload):
//MODEL CLASSES
//-------------
public class Student
{
public int StudentId { get; set; }
public string Name { get; set; }
public virtual ICollection<StudentToCourse> StudentsToCourses { get; set; }
}
public class Course
{
public int CourseId { get; set; }
public string Title { get; set; }
public virtual ICollection<StudentToCourse> StudentsToCourses { get; set; }
}
public class StudentToCourse
{
public int StudentToCourseId { get; set; }
public int FkStudentId { get; set; }
public int FkCourseId { get; set; }
public string Classroom { get; set; }
public virtual Student ObjStudent { get; set; }
public virtual Course ObjCourse { get; set; }
}
Then, here is modelview I need to pass to view
//VIEWMODEL CLASS
//---------------
public class StudentIndexViewModel
{
public IEnumerable<Student> Students { get; set; }
public IEnumerable<Course> Courses { get; set; }
public IEnumerable<StudentToCourse> StudentsToCourses { get; set; }
}
EF does not support conditional include's. You'll need to include all or nothing (ie no Whereinside the Include)
If you need to get the data for just certain relations, you can select it into an anonymous type, something like (the obviously untested);
var intermediary = (from course in db.Courses
from stc in course.StudentsToCourses
where stc.ObjStudent.FkStudentId == id.Value
select new {item, stc}).AsEnumerable();
Obviously, this will require some code changes, since it's no longer a straight forward Course with a StudentsToCourses collection.
I have set up 3 models, code first and the relationships seem to be working but one is causing me a problem.
I have Article, Language and Edition Classes
public class Article
{
public int ID { get; set; }
public string Name { get; set; }
public string Icon { get; set; }
}
public class Language
{
public int ID { get; set; }
public string Name { get; set; }
public string Code { get; set; }
}
public class Edition
{
public int ID { get; set; }
public Article Article { get; set; }
public Language Language { get; set; }
public string Title { get; set; }
public string Details { get; set; }
}
In my bootstrap/DBinitialiser, I can create Objects and populate them fine. The DB is created and the foreign keys for Language and Article are both present on the Edition table and correctly entered.
var engLang = new Language() {Code="en", Name="English Language"};
var altLang = new Language() {Code="xx", Name="Alternative Language"};
db.Languages.Add(engLang);
db.Languages.Add(altLang);
db.SaveChanges();
var testArt = new Article() { Name = "test" };
db.Articles.Add(testArt);
db.SaveChanges();
db.Editions.Add(new Edition(){Article = testArt, Language = engLang, Title="English Content"});
db.Editions.Add(new Edition(){Article = testArt, Language = altLang, Title="Alternative Content"});
db.SaveChanges();
I can now query the Editions and return a list of them, but the Language attribute is always NULL. The Article Attribute works fine.
var query = db.Editions.Where(r => r.Article.ID == Article.ID);
foreach (Edition item in query)
{
// item.Language => NULL
// item.Article => {Object Article}
}
I'm new to .net and Entity-Framework and can't work out why I always get this error.
I can even query by r => r.Language.ID == 1 and still get a NULL attribute on the Edition object.
Make sure you are using EF codefirst in right manner. Here you have some ambiguities. You must determine what relationships actually should exist, in your POCOs. Change classes like bellow:
public class Article
{
[Key]
public int ID { get; set; }
public string Name { get; set; }
public string Icon { get; set; }
}
public class Language
{
[Key]
public int ID { get; set; }
public string Name { get; set; }
public string Code { get; set; }
}
public class Edition
{
[Key]
public int ID { get; set; }
public virtual Article Article { get; set; }
public virtual Language Language { get; set; }
public string Title { get; set; }
public string Details { get; set; }
}
With thanks to AmirHossein Mehrvarzi for helping me write my models more clearly, I believe this error to be caused by the lazy loading of entities while iterating through the result of the query. ref: Entity Framework: There is already an open DataReader associated with this Command.
Without enabling MultipleActiveResultSets I simply added an Include statement to my linq
var query = db.Editions.Where(r => r.Article.ID == Article.ID).Include(r => r.Language);
foreach (Edition item in query)
{
// item.Language => {Object Language}
// item.Article => {Object Article}
}