Getting carousel data back into object - xamarin

I am creating a dynamic carousel view in my Xamarin app, and so far it works just fine, but...
My carousel contains students and each carousel page is a link to a student info page. I want to be able to set an object with the current selected student for me to grab on all the students subpages (hope this makes sense :-/).
My script is as follow.
StudentModel:
public class StudentData
{
public string id { get; set; }
public string name { get; set; }
public string course { get; set; }
public string schoolclass { get; set; }
public string profileImage { get; set; }
}
CarouselPart:
ObservableCollection<StudentData> collection = new ObservableCollection<StudentData>();
collection.Add(new StudentData { name = "Soren Hanson", schoolclass = "4. grade", course = "Math" });
collection.Add(new StudentData { name = "Michael Trane", schoolclass = "7. grade", course = "English" });
collection.Add(new StudentData { name = "Tammy Jump", schoolclass = "1. grade", course = "English" });
DataTemplate template = new DataTemplate(() =>
{
var imageBtn = new Button();
imageBtn.Image = "Images/default.png";
imageBtn.Clicked += delegate {
// ADDING THE CURRENT STUDENT TO MY CURRSTUDENT OBJECT //
//App.currStudent = collection.......
var menteeOptions = new MenteeOptions();
imageBtn.Navigation.PushAsync(menteeOptions);
}
}
carousel.ItemTemplate = template;
carousel.PositionSelected += pageChanged;
carousel.ItemsSource = collection;
Hoping for help with this and thanks in advance :-)

Well you question was quite confusing at first but I will answer it from what I understood you want to keep the selected student object with you on your subpages:
So you can either use SQLite for it which can be found here
Or you can just maintain it as a static system object on your app.xaml.cs and use it
Something like this
App.Xaml.cs
public static object YourDataHolder {get; set;}
In your clicked event:
imageBtn.Clicked += delegate {
// ADDING THE CURRENT STUDENT TO MY CURRSTUDENT OBJECT //
App.YourDataHolder = _yourCollection;
var menteeOptions = new MenteeOptions();
imageBtn.Navigation.PushAsync(menteeOptions);
}
The use it something like this :
fooObject=App.YourDataHolder as FooType;

Related

RavenDB, Linq: Build an expression from a Property inside a nested hierarchy

I stored the objects of the following classes in a ravendb database:
public class Continent
{
public string Id { get; set; }
public string Name { get; set; }
public List<Country> Countries { get; set; }
}
public class Country
{
public string Name { get; set; }
public List<Province> Provinces { get; set; }
}
public class Province
{
public string Name { get; set; }
public List<City> Cities { get; set; }
}
public class City
{
public string Name { get; set; }
public string Address { get; set; }
}
I want to write a method that searches Continents having a specific city. The latter is a parameter of my method. In this method, I want to execute a dynamic query like the following: query= session.Query().Where(ConditionOnTheSearchedCity). But I can not formulate the Expression "ConditionOnTheSearchedCity" because I can not iterate till the Name of each City. In fact, to create an expression based on the Name of the City, I've tried the following which is not working:
ParameterExpression parameterExpression = Expression.Parameter(typeof(Continent), "p");
Expression NameExpression = Expression.PropertyOrField(
Expression.PropertyOrField(
Expression.PropertyOrField(
Expression.PropertyOrField(parameterExpression, "Countries"), "Provinces"),
"Cities"),
"Name");
Can you please help me? Thanks in advance
Why are you going to all the trouble of dynamically building Linq?
Why not just use the RavenDB's DocumentQuery API which allows you to easily build queries dynamically?
As I mentioned in the comments, the question is too broad, so I'll give you just a starting point by providing an example. For more information, take a look at How to: Use Expression Trees to Build Dynamic Queries.
Let have a parameter string cityName and want a filter like this
Expression<Func<Continent, bool>> filter = continent =>
continent.Countries.Any(country =>
country.Provinces.Any(province =>
province.Cities.Any(city => city.Name == cityName)));
It can be build dynamically like this
var city = Expression.Parameter(typeof(City), "city");
var cityCondition = Expression.Equal(Expression.PropertyOrField(city, "Name"), Expression.Constant(cityName));
var province = Expression.Parameter(typeof(Province), "province");
var provinceCondition = Expression.Call(
typeof(Enumerable), "Any", new[] { city.Type },
Expression.PropertyOrField(province, "Cities"),
Expression.Lambda(cityCondition, city));
var country = Expression.Parameter(typeof(Country), "country");
var countryCondition = Expression.Call(
typeof(Enumerable), "Any", new[] { province.Type },
Expression.PropertyOrField(country, "Provinces"),
Expression.Lambda(provinceCondition, province));
var continent = Expression.Parameter(typeof(Continent), "continent");
var continentCondition = Expression.Call(
typeof(Enumerable), "Any", new[] { country.Type },
Expression.PropertyOrField(continent, "Countries"),
Expression.Lambda(countryCondition, country));
var filter = Expression.Lambda<Func<Continent, bool>>(continentCondition, continent);

The entity or complex type 'AdventureWorks2012Model.Product' cannot be constructed in a LINQ to Entities query

As you can see, I got this error when I built Data Gird using Kendo UI. Does anybody could point out where I'm wrong in my code below.
private IEnumerable<Product> GetSubProduct()
{
var context = new AdvenDBEntities();
var subcate = context.Products.Select(p => new Product
{
ProductID = p.ProductID,
Name = p.Name,
Color = p.Color,
ListPrice = p.ListPrice,
}).ToList();
return subcate;
}
Error:
The entity or complex type 'AdventureWorks2012Model.Product' cannot be constructed in a LINQ to Entities query.
Thank you so much for your time!
Since Product is an entity of model, you are creating new object of this entity while selecting the records, which is NOT good idea, I am NOT sure how model will handle this kind of behaviour that is why it is preventing you to do so, (I guess). Anyway you can change the code to this,
private IEnumerable<Product> GetSubProduct()
{
var context = new AdvenDBEntities();
var subcate = context.Products.ToList();
return subcate;
}
BTW your function name indicating that you are missing a Where clause.
Also you can create some custom DTO class and use it instead.
E.g.
class ProductDTO
{
public int ProductID { get; set; }
public string Name { get; set; }
public string Color { get; set; }
public decimal ListPrice { get; set; }
}
private IEnumerable<ProductDTO> GetSubProduct()
{
var context = new AdvenDBEntities();
var subcate = context.Products.Select(p => new ProductDTO
{
ProductID = p.ProductID,
Name = p.Name,
Color = p.Color,
ListPrice = p.ListPrice,
}).ToList();
return subcate;
}
The first bad smell code I can point out for you. DBContext implements IDisposable so you are responsible for calling Dispose on it. In all, but one case in here, using block
You must build query to get all the product and then extract from it.
private IEnumerable<Product> GetSubProduct()
{
using (var context = new AdvenDBEntities())
{
// Get all constructed type product and then select from it
var subcate = context.Products
.ToList()
.Select(p => new Product
{
ProductID = p.ProductID,
Name = p.Name,
Color = p.Color,
ListPrice = p.ListPrice,
});
return subcate;
}
}

Getting an Enum to display on client side

I'm having hard time understanding how to convert an Enum value to it's corresponding name. My model is as follows:
public class CatalogRule
{
public int ID { get; set; }
[Display(Name = "Catalog"), Required]
public int CatalogID { get; set; }
[Display(Name = "Item Rule"), Required]
public ItemType ItemRule { get; set; }
public string Items { get; set; }
[Display(Name = "Price Rule"), Required]
public PriceType PriceRule { get; set; }
[Display(Name = "Value"), Column(TypeName = "MONEY")]
public decimal PriceValue { get; set; }
[Display(Name = "Exclusive?")]
public bool Exclude { get; set; }
}
public enum ItemType
{
Catalog,
Category,
Group,
Item
}
public enum PriceType
{
Catalog,
Price_A,
Price_B,
Price_C
}
A sample result from .net API:
[
{
$id: "1",
$type: "XYZ.CMgr.Models.CatalogRule, XYZ.CMgr",
ID: 1,
CatalogID: 501981,
ItemRule: 0,
Items: "198",
PriceRule: 1,
PriceValue: 0.5,
Exclude: false
},
{
$id: "2",
$type: "XYZ.CMgr.Models.CatalogRule, XYZ.CMgr",
ID: 2,
CatalogID: 501981,
ItemRule: 2,
Items: "9899",
PriceRule: 2,
PriceValue: 10.45,
Exclude: false
}
]
So in this example, I need to get Catalog for results[0].ItemRule & Price A for results[0].PriceRule. How can I accomplish this in BreezeJS??
This is easy to do in ASP.NET Web API, because it is an out-of-box feature in the default JSON serializer (Json.NET).
To see strings instead of enum numbers in JSON, just add an instance of StringEnumConverter to JSON serializer settings during app init:
var jsonFormatter = GlobalConfiguration.Configuration.Formatters.JsonFormatter;
jsonFormatter.SerializerSettings.Converters.Add(new Newtonsoft.Json.Converters.StringEnumConverter());
UPDATE: Yep, you right, this is not help with Breeze.js. Ok, you can anyway do a little magic to make enums work like strings (while new version with fix is not released).
Create a custom ContextProvider which updates all integer enum values in metadata to strings. Here it is:
public class StringEnumEFContextProvider<T> : EFContextProvider<T>
where T : class, new()
{
protected override string BuildJsonMetadata()
{
XDocument xDoc;
if (Context is DbContext)
{
xDoc = GetCsdlFromDbContext(Context);
}
else
{
xDoc = GetCsdlFromObjectContext(Context);
}
var schemaNs = "http://schemas.microsoft.com/ado/2009/11/edm";
foreach (var enumType in xDoc.Descendants(XName.Get("EnumType", schemaNs)))
{
foreach (var member in enumType.Elements(XName.Get("Member", schemaNs)))
{
member.Attribute("Value").Value = member.Attribute("Name").Value;
}
}
return CsdlToJson(xDoc);
}
}
And use it instead of EFContextProvider in your Web API controllers:
private EFContextProvider<BreezeSampleContext> _contextProvider =
new StringEnumEFContextProvider<BreezeSampleContext>();
This works well for me with current Breeze.js version (1.1.3), although I haven't checked other scenarios, like validation...
UPDATE: To fix validation, change data type for enums in breeze.[min|debug].js, manually (DataType.fromEdmDataType function, dt = DataType.String; for enum) or replace default function during app init:
breeze.DataType.fromEdmDataType = function (typeName) {
var dt = null;
var parts = typeName.split(".");
if (parts.length > 1) {
var simpleName = parts[1];
if (simpleName === "image") {
// hack
dt = DataType.Byte;
} else if (parts.length == 2) {
dt = DataType.fromName(simpleName);
if (!dt) {
if (simpleName === "DateTimeOffset") {
dt = DataType.DateTime;
} else {
dt = DataType.Undefined;
}
}
} else {
// enum
dt = DataType.String; // THIS IS A FIX!
}
}
return dt;
};
Dirty, dirty hacks, I know... But that's the solution I found
There will be a new release out in the next few days where we "change" breeze's enum behavior ( i.e. break existing code with regards to enums). In the new release enums are serialized and queried by their .NET names instead of as integers. I will post back here when the new release is out.

MVC populate dropdown from foreign key

I have been struggling with this for several days. I need to populate a dropdownlistfor with genres.
My MovieRepository to grab the genres:
public IQueryable<Movies> MoviesAndGenres
{
get { return db.Movies.Include(m => m.parentGenre); }
}
My movie model
public virtual Genres parentGenre { get; set; }
Genre Model:
public class Genres
{
public Genres()
{
this.movies = new HashSet<Movies>();
}
[Key]
public int genreId { get; set; }
[Required(ErrorMessage = "A genre name is required")]
[StringLength(25)]
public String genreName { get; set; }
public ICollection<Movies> movies { get; set; }
}
I am trying to pass in the genres with a select list, but I am getting a LINQ to Entities does not recognize the System.String To String() Method, and this method cannot be translated to a stored expression.
Movies Controller, addMovie action:
ViewBag.Genres = movieRepository.MoviesAndGenres.Select(m => new SelectListItem
{
Text = m.parentGenre.genreName,
Value = m.parentGenre.genreId.ToString()
}).ToList();
return View();
View:
#Html.DropDownListFor(m => m.parentGenre, (SelectList)ViewBag.Genres)
Any help would be greatly appreciated!
Update:
Repository:
public IQueryable<Genres> MoviesAndGenres
{
get { return db.Genres; }
}
Controller:
var x = movieRepository.MoviesAndGenres.Select(m => new
{
Text = m.genreName,
Value = m.genreId
});
ViewBag.Genres = new SelectList(x);
return View();
View:
#Html.DropDownListFor(m => m.parentGenre, (SelectList)ViewBag.Genres)
Since you're retrieving all of the records anyways, you can just do this.
ViewBag.Genres = movieRepository.MoviesAndGenres.AsEnumerable()
.Select(m => new SelectListItem
{
Text = m.parentGenre.genreName,
Value = m.parentGenre.genreId.ToString()
});
You would also need to change your view to:
#Html.DropDownListFor(m => m.parentGenre, new SelectList(ViewBag.Genres))
Actually, a better approach would probably be this, since then it only retrieves the specific columns you need:
var x = movieRepository.MoviesAndGenres.Select(m => new
{
Text = m.parentGenre.genreName,
Value = m.parentGenre.genreId
});
ViewBag.Genres = new SelectList(x)
Also, the ToList() is no longer required because it's already in a an immediate state.

Trouble filling and using MultiSelectList/ListBoxFor in ASP.NET MVC 3

I'm trying to adapt the answers for filling a ListBoxFor that has preselected values that I've found here on SO and am having some trouble with the adaptation.
This is one of the questions I've been referring to: here
Here is my class that defines a list object
public class SelectListDTO {
public int ID { get; set; }
public string Name { get; set; }
}
I have a method on a class that fills a List of SelectListDTO items. The CheckRefresh checks to see if the cache is expired, if so it refills the cache. So this method gets my list:
private List<SelectListDTO> GetSelectList() {
CheckRefresh();
var lst = new List<SelectListDTO>(_cache.Count + 1);
_cache.ForEach(item => lst.Add(new SelectListDTO { ID = item.ID, Name = item.Name }));
return lst;
}
My Model is define with these Properties/Methods:
public class MyModel {
[Required]
[Display(Name = "Program Type")]
[Min(1, ErrorMessage = "Please select a Program Type")]
public int[] SelectedProgramTypes { get; set; }
public MultiSelectList ProgramTypes { get; set; }
public MyModel() {
PopulateProgramTypeList();
}
private void PopulateProgramTypeList() {
// Get all available list items
var programTypes = ProgramTypeService.Instance.GetSelectList;
// how to fill multiselectlist with my List<SelectListDTO> items;
ProgramTypes = new MultiSelectList(??)
}
}
1st part of question is from above here^ How to fill the MultiSlectList with my List of SelectListDTO objects
Also in my controller action I am getting the saved items from the DB and will need to pass them to the model as SelectedProgramTypes. This is currently in my action:
public ActionResult Edit(int? id) {
// Code here to validate id and that user is associated with id
lenderProduct = new LenderProduct(id);
var model = BuildModel(lenderProduct); // returns instance or MyModel
var selectedProgramTypes = lenderProduct.ProgramTypes;
foreach (var item in selectedProgramTypes) {
/// How to fill the Model.SelectedProgramTypes array
}
return View(model);
}
2nd part of question is how to get the currently selected items that I read from the DB into the array that can be used by the MultiSelectList in the Model
I feel like I'm this close but am missing some pattern or hopefully just the correct syntax into getting this to work in this way as opposed to the ways I've seen posted here.
I haven't made it to the View yet but from what I've seen that is just as easy as filling a normal DropDownList.
1st part of question is from above here^ How to fill the
MultiSlectList with my List of SelectListDTO objects
ProgramTypes = new MultiSelectList(programTypes.Select(x => new SelectListItem
{
Value = x.ID.ToString(),
Text = x.Name
}));
2nd part of question is how to get the currently selected items that I
read from the DB into the array that can be used by the
MultiSelectList in the Model
It's not clear how your LenderProduct class looks like but assuming the ProgramTypes property is just an array of integers you could directly assign it to your view model:
public ActionResult Edit(int? id)
{
// Code here to validate id and that user is associated with id
var lenderProduct = new LenderProduct(id);
var model = BuildModel(lenderProduct); // returns instance or MyModel
model.SelectedProgramTypes = lenderProduct.ProgramTypes;
return View(model);
}
and if it is an array of some complex object you could select the corresponding property that contains the id:
public ActionResult Edit(int? id)
{
// Code here to validate id and that user is associated with id
var lenderProduct = new LenderProduct(id);
var model = BuildModel(lenderProduct); // returns instance or MyModel
model.SelectedProgramTypes = lenderProduct.ProgramTypes.Select(x => x.ID).ToArray();
return View(model);
}

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