LINQ-to-Entities WHERE condition not executed on sql server - asp.net

I have followed the book of Adam Freeman to learn about ASP.NET MVC 5. I have implemented the repository pattern as described in the book. I'm using WHERE and log the SQL commands with the SQL-EventProfiler, then I will see no WHERE condition.
This is my example code, for the repository I have used Ninject:
public interface IHelpRepository {
IEnumerable<Help> Helps { get; }
}
public class HelpRepository : IHelpRepository {
private HelpDBContext context = new HelpDBContext();
public IEnumerable<Help> Helps {
get { return context.Helps; }
}
}
public class Help {
[Required]
[Key]
public int Id { get; set; }
[Required]
public string Title { get; set; }
[Required]
public string Description { get; set; }
}
public class HelpController : Controller {
private IHelpRepository HelpRepository;
public HelpController (IHelpRepository helpRepository) {
this.HelpRepository= helpRepository;
}
public ActionResult HelpDescription(int Id) {
Help help = helpRepository.Helps.Where(h => h.Id == Id).SingleOrDefault<Help>();
return View("HelpDescription", help);
}
}
The resulting SQL-Command (XEventProfiler):
SELECT [Extent1].[Id] AS [Id], [Extent1].[Title] AS [Title], [Extent1].[Description] AS [Description] FROM [dbo].[Helps] AS [Extent1]
Why is the WHERE not included in the resulting SQL command?

public IEnumerable Helps {
get { return context.Helps; }
}
You are returning IEnumerable here and at this point the query gets executed. There are two things you can get away with it
First option is to return IQueryable and use where filter and then check profiler like this
public IQueryable<Help> Helps {
get { return context.Helps; }
}
Help help = helpRepository.Helps.Where(h => h.Id == Id).SingleOrDefault<Help>();
Second method is to create a repository method which filters in the the method and returns IEnumerable
public IEnumerable<Help> Where(Expression<Func<Help,bool>> where)
{
return context.Helps.Where(where);
}
To understand the difference between IQueryable and IEnumerable just go through the following link
IQueryable vs IEnumerable
IQueryable always perform queries on the data source context while IEnumerable works in memory, after data gets fetched from data source provider

Related

EF Core with CosmosDB: OwnsOne and OwnsMany throw NullReferenceException

I'm working on a new project that uses CosmosDB and Entity Framework Core (via the Microsoft.EntityFrameworkCore.Cosmos NuGet package, version 5.0.7; the project itself is .NET Core 5). I'm new to both, and running into an issue I can't sort out.
In short, I need to save a complex object to the database. It's a big model that will have multiple collections of classes underneath it, each with their own properties and some with collections underneath them as well. I'm trying to configure EF with OwnsOne and OwnsMany to store these child objects underneath the top-level one. The code compiles, and will save to the database so long as all the owned objects are left empty. But whenever I put anything into an owned object, either with OwnsOne or OwnsMany, I get a pair of NullReferenceExceptions.
I've tried to strip my code down to the very basics. Here's how it currently looks.
Owner and owned classes:
public class Questionnaire
{
// Constructors
private Questionnaire() { }
public Questionnaire(Guid id)
{
Test = "Test property.";
TV = new TestQ();
Id = id;
}
public Guid Id { get; set; }
public string Test { get; set; }
public TestQ TV { get; set; }
// Public Methods
public void AddForm(Form f)
{
// not currently using this method
//Forms.Add(f);
}
}
public class TestQ
{
public TestQ()
{
TestValue = "test ownsone value";
}
public string TestValue { get; set; }
}
DbContext:
public class QuestionnaireDbContext : DbContext
{
public DbSet<Questionnaire> Questionnaires { get; set; }
public QuestionnaireDbContext(DbContextOptions<QuestionnaireDbContext> options) : base(options) { }
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.HasDefaultContainer(nameof(Questionnaires));
modelBuilder.Entity<Questionnaire>().HasKey(q => q.Id);
modelBuilder.Entity<Questionnaire>().OwnsOne(q => q.TV);
}
}
And the code from the service that calls the dbContext (note that this is based on a generic service that I didn't set up originally). The actual exceptions are thrown here.
public virtual TEntity Add(TEntity entity)
{
_context.Entry(entity).State = EntityState.Added;
_context.SaveChanges();
return entity;
}
Ultimately I need this to work with OwnsMany and a collection, but I figured it might be simpler to get it working with OwnsOne first. The key thing to note here is that if I comment out the line
TV = new TestQ();
in the Questionnaire class, the model persists correctly into CosmosDB. It's only when I actually instantiate an owned entity that I get the NullReferenceExceptions.
Any advice would be much appreciated! Thank you!
Well, I'm not sure why this is the case, but the issue turned out to be with how we were adding the document. Using this generic code:
public virtual async Task<TEntity> Add(TEntity entity)
{
_context.Entry(entity).State = EntityState.Added;
await _context.SaveChanges();
return entity;
}
was the issue. It works just fine if I use the actual QuestionnaireDbContext class like so:
context.Add(questionnaire);
await context.SaveChangesAsync();

How to specify default property values for owned entity types in Entity Framework Core 2.0?

I have a simple POCO type, say something like
public class OwnedEntity {
public string stringProperty { get; set; }
public decimal decimalProperty { get; set; }
public bool boolProperty { get; set; }
public int intProperty { get; set; }
}
and an actual entity with an OwnedEntity reference
public class SomeEntity {
public string Id { get; set; }
public OwnedEntity OwnedEntity { get; set; }
}
I set up the relationship like described in the documentation using EF Core's Fluent API:
protected override void OnModelCreating (ModelBuilder builder) {
base.OnModelCreating (builder);
builder.Entity<SomeEntity> ().OwnsOne (e => e.OwnedEntity);
}
I can't find anything on how to define default-values for all the properties of OwnedEntity. I tried to initialize the properties like this:
public class OwnedEntity {
public string stringProperty { get; set; } = "initial"
public decimal decimalProperty { get; set; } = -1M;
public bool boolProperty { get; set; } = false;
public int intProperty { get; set; } = -1;
}
but with no effect. Same goes with the [DefaultValueAttribute] (but that was to expect since it's explicitly mentioned).
There's a bit of information on how to handle initial values for regular entities:
modelBuilder.Entity<SomeOtherEntity>()
.Property(e => e.SomeIntProperty)
.HasDefaultValue(3);
But since I'm facing an Owned Entity Type, I can't access the type via Entity<T>.
Is there a way of doing what I'm looking for?
Some things worth mentioning:
I have a solid amount of specific entities where most of them are using the OwnsOne relation
Declaring all OwnedEntity-properties in a base class is not an option since not all the entities have those properties
I`m using EF Core 2.0.3 and ASP.NET Core MVC 2.0.4
Edit:
Originally, I wanted to have newly created SomeEntity instances to come with preset properties for all of the 'embedded' SomeEntity.OwnedEntity properties.
But looking at how my associated controller works, it all makes sense... I have the following methods for the 'Create' operation:
[HttpGet]
public IActionResult Create () {
return View (nameof (Create));
}
[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Create (SomeEntity model) {
context.Add (model);
await context.SaveChangesAsync ();
// redirect etc.
}
Which means that no object is created for the [HttGet] overload of Create and all the HTML inputs linked to properties (via asp-for) are initially empty. Okay. So I guess the proper way of doing this is to manually create a new instance of SomeEntity and pass it to the Create view like this:
[HttpGet]
public IActionResult Create () {
return View (nameof (Create), new SomeEntity());
}
Is this the right approach then or are there some more things to keep in mind?
Assuming you understand what EF Core Default Values are for, and just looking for equivalent of Entity<T>().Property(...) equivalent.
The owned entities are always configured for each owner type by using the ReferenceOwnershipBuilder<TEntity,TRelatedEntity> class methods. To access this class you either use the result of OwnsOne method, or use the OwnsOne overload taking second argument of type Action<ReferenceOwnershipBuilder<TEntity,TRelatedEntity>>.
For instance, using the second approach:
builder.Entity<SomeEntity>().OwnsOne(e => e.OwnedEntity, ob =>
{
ob.Property(e => e.stringProperty)
.HasDefaultValue("initial");
ob.Property(e => e.decimalProperty)
.HasDefaultValue(-1M);
// etc.
});

POST Method fails to populate request object in ServiceStack

I've been using service stack for a while and came upon a scenario where the POST method uses the default instance of the IReturn object (with all the properties defaulting to their datatype values). The values supplied as part of the Route (/product/1234345/) are the only ones populated. I've laid out an example below:
[Route("/search/{searchMethod}/books")]
public class SearchRequest : IReturn<SearchResponse>
{
public SearchProvider searchProvider { get; set; }
public string searchTerm { get; set; }
public string categoryID { get; set; }
public long maxResults { get; set; }
//Only this property gets populated if method is post
public string searchMethod { get; set; }
}
public SearchResponse Any(SearchRequest searchRequest)
{
//This works only for non-post requests
return Put(searchRequest);
}
public SearchResponse Get(SearchRequest searchRequest)
{
//This works
return Put(searchRequest);
}
public SearchResponse Post(SearchRequest searchRequest)
{
//This does not
return Put(searchRequest);
}
public SearchResponse Put(SearchRequest searchRequest)
{
//Code for put method goes here
}
I'm then using a client to call these methods
SearchServiceClient searchClient = new SearchServiceClient(SearchServiceAPIUrl);
SearchResponse searchResponse = searchClient.Search(SearchProvider.SampleSearchProvider, searchterm, categoryID, 100,"conservative");
Any help is really appreciated
Thanks
I've always just populated my request object in the constructor and sent it to the service
searchClient.Post(new SearchRequest(SearchProvider.SampleSearchProvider,
searchterm, categoryID, 100,"conservative")):
I finally found the solution after tinkering with the DTO. It seems for post requests all DTO properties needed to have a [DataMember] attribute for serialization/deserialization and make sure that the class also has a [DataContract] attribute.

How to get the mysql data in ASP.net MVC3?

I'm trying to get my mysql data in ASP.net MVC3.
The mysql Database Name is supply_db and table name is xcart_orders.
ASP.net code is like below,
(Im just following my book, and just switch to my DB info but it does not work :( )
(I will omit using and namespace)
Web.Config File,
<add name="EFMysqlContext" connectionString="server=XXX.XXX.XXX.XX;User Id=root;pwd=xxx;Persist Security Info=True;database=supply_db"
providerName="Mysql.Data.MySqlClient" />
Abstract/IXcartOrdersRepository.cs
public interface IXcartOrdersRepository
{
IQueryable<XcartOrder> xcart_orders { get; }
}
/Concrete/EFXcartOrderRepository.cs
public class EFXcartOrdersRepository : IXcartOrdersRepository
{
private EFMysqlContext context = new EFMysqlContext();
public IQueryable<XcartOrder> xcart_orders
{
get { return context.xcart_orders; } // I thought the 'xcart_orders' should be match with db table name, isn't it?
}
}
/Entities/XcartOrder.cs
public class XcartOrder
{
[Key]
public int orderid { get; set; }
public string login { get; set; }
public string membership { get; set; }
public decimal subtotal { get; set; }
}
and In my controller,
IXcartOrdersRepository XcartOrdersRepository = new EFXcartOrdersRepository();
int orderCnt = XcartOrdersRepository.xcart_orders.Count();
then error occur, the error message say "{"Table 'supply_db.XcartOrders' doesn't exist"}"
I think I could connect to db, but couldn't get the table.
anybody know which part do I need to change?
Thank you!
can you decorate your Xcartorder class with the Table attribute to explicitly specify the desired name?
[Table("xcart_orders")]
public class XcartOrder
{
...
edit: attribute syntax

Populate dropdownlist from another dropdownlist with objects in MVC 2

I am trying to develop a simple MVC 2 timesheet application for my small business.
I have a sort of mock model for now until I have a database in place, just to make things simpler while I develop the functionality. It consists of the following:
public class CustomersRepository
{
public CustomersRepository()
{
Customers = new List<Customer>();
}
public List<Customer> Customers { get; set; }
}
public class Task
{
public Task()
{
Customer = new Customer();
TimeSegments = new List<TimeSegment>();
}
public override string ToString()
{
return Name;
}
public string Name { get; set; }
public Customer Customer { get; set; }
public List<TimeSegment> TimeSegments { get; set; }
}
public class TimeSegment
{
public string Id { get; set; }
public string Date { get; set; }
public int Hours { get; set; }
}
public class Customer
{
//To show the name in the combobox instead of the object name.
public override string ToString()
{
return Name;
}
public Customer()
{
Tasks = new List<Task>();
}
public List<Task> Tasks { get; set; }
public string Name { get; set; }
}
I initialize the repository in the controller, and pass the "model" to the view:
CustomersRepository model = new CustomersRepository();
public ActionResult Index()
{
InitializeRepository();
return View(model);
}
Now, in the view I populate a dropdownlist with the customers:
<div>
<%:Html.DropDownListFor(m => m.Customers, new SelectList(Model.Customers), new {#id="customerDropDownList"}) %>
</div>
But then I need to populate a second dropdownlist (taskDropDownList for the tasks associated with a particular customer) based on the selection the user chooses in the customer dropdownlist.
But how do I do this exactly? I have seen examples with jQuery, but I'm not sure how to apply them to this situation. Also, the examples seem to just populate the lists with string values. I need to be able to access the objects with all their properties. Because the next thing I need to do is to be able to populate the TimeSegments list of the selected task with values from input fields (i.e. the hours worked for particular dates). And for that to be saved to the "model" (eventually to the database) in the controller, how do I get it there, unless the objects are all part of the same model bound to the View?
I'm on rather thin ice with this since I still find the connection between the View and the Controller hard to handle, compared with e.g. Windows development, where these things are rather easy to do. So I would really appreciate a good step by step example if anyone would be so kind as to provide that!
I found the answer here:
http://www.pieterg.com/post/2010/04/12/Cascading-DropDownList-with-ASPNET-MVC-and-JQuery.aspx
It needed some tweaks, and I got help here from CGK. See this post:
Cascading dropdownlist with mvc and jQuery not working

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