here is my table:
table name: data
fields:
Id
category
description
imagePath
I'm building a webApi that returns all imagePath or by id.
web api controller:
namespace task.Controllers
{
public class ImagesController : ApiController
{
DataEntry db = new DataEntry();
public IEnumerable<datum> GetImages()
{
var imagePath = from m in db.data select m;
return imagePath;
}
public IHttpActionResult GetImages(int id)
{
var imagePath = from m in db.data select m;
var imagPath = imagePath.Where((p) => p.Id == id);
if (imagePath == null)
{
return NotFound();
}
return Ok(imagePath);
}
}
}
It's returning all fields (Id,category, description and imagePath) instead of imagePath only.and for the select by Id method it's not working also, so what is wrong??
For the imagePath, try specifying it in the linq query like so:
public IEnumerable<string> GetImages()
{
var imagePath = from m in db.data select m.imagePath;
return imagePath.ToList();
}
For the select by id, try this:
public string GetImages(int id)
{
var imagePath = from m in db.data select m;
var imagPath = imagePath.Where((p) => p.Id == id);
if (imagPath == null)
{
return NotFound();
}
return Ok(imagPath.imagePath);
}
Double check for typo such as imagPath and imagePath too
Related
I met an error display when I tried to access user contact to fetch all contacts: The splash screen hide the permission dialog.
Did anyone meet this error before?
Interface:
public interface IUserContactsService
{
List<PhoneContactInfo> GetAllPhoneContacts(IEnumerable<int> filterIds = null);
}
UserContactService.cs:
[assembly: Dependency(typeof(UserContactService))]
namespace Test.iOS
{
public class PhoneContact
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string PhoneNumber { get; set; }
public string Name { get => $"{FirstName} {LastName}"; }
}
public class UserContactService : IUserContactsService
{
string phoneNumber(string number)
{
string callNumber = number;
int i = 0;
while (i < callNumber.Length)
{
if (callNumber[i] == ' ' || callNumber[i] == 160 || callNumber[i] == '-')
callNumber = callNumber.Remove(i, 1);
else
i++;
}
return callNumber;
}
public List<PhoneContactInfo> GetAllPhoneContacts(IEnumerable<int> filterIds = null)
{var keysTOFetch = new[] { CNContactKey.GivenName, CNContactKey.FamilyName, CNContactKey.EmailAddresses };
NSError error;
CNContact[] contactList;
var ContainerId = new CNContactStore().DefaultContainerIdentifier;
using (var predicate = CNContact.GetPredicateForContactsInContainer(ContainerId))
using (var store = new CNContactStore())
{
contactList = store.GetUnifiedContacts(predicate, keysTOFetch, out error);
}
var contacts = new List<PhoneContactInfo>();
foreach (var item in contactList)
{
if (null != item && null != item.EmailAddresses)
{
contacts.Add(new PhoneContactInfo
{
contactName = item.GivenName,
contactNumber = item.PhoneNumbers.ToString()
});
}
}
return contacts;
}
}
Here is my solution:
public List<PhoneContactInfo> GetAllPhoneContacts (IEnumerable<int> filterIds = null)
{
// if the app was not authorized then we need to ask permission
if (ABAddressBook.GetAuthorizationStatus() == ABAuthorizationStatus.Authorized)
{
GetContacts();
}
else Console.WriteLine("Error");
}
I have a class:
public class Employee
{
public int Id { get; set; }
public string Name { get; set; }
public int Salary { get; set; }
public string Address {get;set;}
}
And query using Entity Framework is:
var selectedEmployee = entities.Employees
.Where(e=>e.Salary>10000)
.Select(emp => new EmpDTO
{
Id = emp.Id,
Name = emp.Name,
Salary = emp.Salary
});
My question is:
I want to allow extending this query without rewriting the base query. It should allow adding a new field in the .Select(.....) by extending the above query.
Without rewriting the complete query:
var selectedEmployee = entities.Employees
.Where(e=>e.Salary>10000)
.Select(emp => new EmpDTO
{
Id = emp.Id,
Name = emp.Name,
Salary = emp.Salary,
Address = emp.Address
});
How can I do that?
Thanks
If I understand, you can try this:
public IQuerable<EmpDTO> GetEmployee(Func<Employee, EmpDTO> projection = null)
{
if(projection == null)
projection = emp => new EmpDTO {
Id = emp.Id,
Name = emp.Name,
Salary = emp.Salary,
};
return entities.Employees.Where(e => e.Salary > 10000).Select(projection);
}
Implementation:
var query = classInstance.GetEmployee();
//or
query = classInstance.GetEmployee(emp => new EmpDTO {
Id = emp.Id,
Name = emp.Name,
Salary = emp.Salary,
Address = emp.Address
});
If you always want to get some set of fields, like Id, Name and
Salary and sometimes take additional fields(and specify only their
as method arguments), you should to take all fields from DB and only
then filter them depends on your condition - it is bad practice to do
SELECT *, so you should get default set of fields or specify all desired fields mannualy.
Solution with SELECT *:
public List<EmpDTO> GetEmployee(Func<Employee, EmpDTO> projection)
{
var query = entities.Employees.Where(e => e.Salary > 10000).ToList().Select(x => {
var item = projection == null ? new EmpDTO() : projection(x);
item.Id = x.Id;
item.Name = x.Name;
item.Salary = x.Salary;
return item;
}).ToList();
}
At this case return value is List<T> not IQuerable<T>;
Implementation:
var items = classInstance.GetEmployee(emp => new EmpDTO { Address = emp.Address });
//items also will contain fields: Id, Name and Salary by default
The following code is taken from the tutorial: http://www.asp.net/mvc/tutorials/getting-started-with-aspnet-mvc3/cs/examining-the-edit-methods-and-edit-view which shows how ASP.net MVC 3 can be used to manage a movie database.
In the tutoral, a list object is added to the controller class that contains every movie genre that exists in the database. This list is then passed to a drop-down in the view enabling the database to be searched by genre.
Controller: (code related to movie genre in bold)
public ActionResult SearchIndex(string movieGenre, string searchString)
{
var GenreLst = new List<string>();
var GenreQry = from d in db.Movies
orderby d.Genre
select d.Genre;
GenreLst.AddRange(GenreQry.Distinct());
ViewBag.movieGenre = new SelectList(GenreLst);
var movies = from m in db.Movies
select m;
if (!String.IsNullOrEmpty(searchString))
{
movies = movies.Where(s => s.Title.Contains(searchString));
}
if (string.IsNullOrEmpty(movieGenre))
return View(movies);
else
{
return View(movies.Where(x => x.Genre == movieGenre));
}
}
What I want to do is enhance this further so that the movies can be searched by price as well as genre. I know I can re-use the much of the same code to do this. I think I need to create a new class that the controller class can pass either the genre or price. Is this correct? IF so, I'd appreciate an example. Thanks.
Update/Clarification:
I want to avoid repeating the code for both genre and price as below:
public ActionResult SearchIndex(string movieGenre, string searchString,float moviePrice)
{
var GenreLst = new List<string>();
var GenreQry = from d in db.Movies
orderby d.Genre
select d.Genre;
GenreLst.AddRange(GenreQry.Distinct());
ViewBag.movieGenre = new SelectList(GenreLst);
var PriceLst = new List<string>();
var PriceQry = from d in db.Movies
orderby d.Genre
select d.Genre;
PriceLst.AddRange(GenreQry.Distinct());
ViewBag.moviePrice = new SelectList(PriceLst);
var movies = from m in db.Movies
select m;
if (!String.IsNullOrEmpty(searchString))
{
movies = movies.Where(s => s.Title.Contains(searchString));
}
if (string.IsNullOrEmpty(movieGenre))
return View(movies);
else
{
return View(movies.Where(x => x.Genre == movieGenre));
}
if (string.IsNullOrEmpty(moviePrice))
return View(movies);
else
{
return View(movies.Where(x => x.Genre == moviePrice));
}
}
You just have to insert a text box in the view to get price value. Then receive this value at action and modify the query to get desired results.
like this:
#Html.ActionLink("Create New", "Create")
#using (Html.BeginForm()){
<p>Genre: #Html.DropDownList("movieGenre", "All")
Title: #Html.TextBox("SearchString")
Price: #Html.TextBox("Price")
<input type="submit" value="Filter" /></p>
}
And in the action method you are using the code below to populate the dropdownlist with genre values. You need not do the same for price value.
var GenreLst = new List<string>();
var GenreQry = from d in db.Movies
orderby d.Genre
select d.Genre;
GenreLst.AddRange(GenreQry.Distinct());
ViewBag.movieGenre = new SelectList(GenreLst);
And in your action method you just have to use the value of price to filter data
public ActionResult SearchIndex(string movieGenre, string searchString,float price)
{
var GenreLst = new List<string>();
var GenreQry = from d in db.Movies
orderby d.Genre
select d.Genre;
GenreLst.AddRange(GenreQry.Distinct());
ViewBag.movieGenre = new SelectList(GenreLst);
var movies = from m in db.Movies
select m;
if (!String.IsNullOrEmpty(searchString))
{
movies = movies.Where(s => s.Title.Contains(searchString));
}
if (string.IsNullOrEmpty(movieGenre))
return View(movies);
else
{
return View(movies.Where((x => x.Genre == movieGenre) &&(x => x.Price== price)));
}
}
You can do it in so many different ways while all are correct but it depends on the complexity of your project. Basically you don't want to over-engineer a simple program. But in general you should move all of your logic to a separate class and use your actions for creating and calling the right logic class:
public class GetMoviesRequest
{
public string Name { get; set; }
public float? Price { get; set; }
}
public class MoviesLogic
{
private List<Movie> Movies;
public IEnumerable<Movie> Get(GetMoviesRequest request)
{
IEnumerable<Movie> filtered = Movies.AsQueryable();
if (!string.IsNullOrEmpty(request.Name))
{
//Filter by name
filtered = filtered.Where(m => m.Name == request.Name);
}
if (request.Price.HasValue)
{
//Filter by value
filtered = filtered.Where(m => m.Price == request.Price);
}
return filtered;
}
}
public class MyController
{
public ActionResult SearchIndex(string movieGenre, string searchString)
{
var logic = new MoviesLogic();
var movies = logic.Get(new GetMoviesRequest() { Name = searchString } )
///do stuff with movies
}
}
I have following code for updating user's column
public void UpdateLastModifiedDate(string username)
{
using (AppEntities db = new AppEntities())
{
var result = from u in db.Users where (u.UserName == username) select u;
if (result.Count() != 0)
{
var dbuser = result.First();
dbuser.LastModifiedDate = DateTime.Now;
db.SaveChanges();
}
}
}
I have other's 2 function of almost same of above function for UpdateLastLogOutDate, UpdateLastLoginDate. So, I decided to define single function for all to update Last Date like:
public void UpdateLastDate(string username, string ColumnName);
Here, I can not put ColumnName variable like this:
dbuser.ColumnName = DateTime.Now;
Is there any other way to do this using LINQ
You could define the method like this:
public void Update(string username, Action<User> action)
{
using (AppEntities db = new AppEntities())
{
var result = from u in db.Users where (u.UserName == username) select u;
if (result.Count() != 0)
{
var dbuser = result.First();
action(dbuser);
db.SaveChanges();
}
}
}
And now there could be different usages of this method:
Update("john", user => user.LastModifiedDate = DateTime.Now);
Update("smith", user => user.UpdateLastLogOutDate = DateTime.Now);
Update("admin", user =>
{
user.LastModifiedDate = DateTime.Now;
user.UpdateLastLogOutDate = DateTime.Now;
});
But if the expression is not known at compile time you may take a look at dynamic LINQ.
You could write your code this way also by sending an instance of your entity as parameter:
public void UpdateLastModifiedDate(Entityclassname ent) //[like if table name is item then Entityclassname should be items etc..]
{
using (AppEntities db = new AppEntities())
{
var result = from u in db.Users where (u.UserName == ent.username) select u;
if (result.Count() != 0)
{
var dbuser = result.First();
dbuser.LastModifiedDate = DateTime.Now;
dbuser.UpdateLastLogOutDate=ent.UpdateLastLogOutDate ;
db.SaveChanges();
}
}
}
It's the first time that I use EmitMapper.
I have a list of object ex: Customer and I would like to map this list in a ienumerable of CustomerDTO how can I do that?
Tnx
It's straightforward if you have a list and want to convert it to list of DTOs:
var mapper = ObjectMapperManager.DefaultInstance.GetMapper<Customer, CustomerDTO>();
IEnumerable<CustomerDTO> dtos = listOfCustomer.Select(mapper.map);
The preblem is when the list is in another object, for example User and UserDTO:
class User {
public List<Customer> Customers { get; set; }
}
class UserDTO {
public IEnumerable<CustomerDTO> Customers { get; set; }
}
It seems that EmitMapper does not support conversion from List to Enumerable. A way to support it would be:
var customerMapper = ObjectMapperManager
.DefaultInstance.GetMapper<Customer, CustomerDTO>();
var mapper = ObjectMapperManager.DefaultInstance
.GetMapper<User, UserDTO>(
new DefaultMapConfig()
.ConvertUsing<List<Customer>, IEnumerable<CustomerDTO>>(
a => a.Select(customerMapper.Map))
);
This can be done creating a custom class, implementing the interface "ICustomConverterProvider" and adding a ConvertGeneric to the "DefaultMapConfig".
Looking on the source code of EmitMapper, i found a class named "ArraysConverterProvider", which is the default generic converter from ICollections to Arrays.
Adapting the code from this class to work with IEnumerable collections:
class GenericIEnumerableConverterProvider : ICustomConverterProvider
{
public CustomConverterDescriptor GetCustomConverterDescr(
Type from,
Type to,
MapConfigBaseImpl mappingConfig)
{
var tFromTypeArgs = DefaultCustomConverterProvider.GetGenericArguments(from);
var tToTypeArgs = DefaultCustomConverterProvider.GetGenericArguments(to);
if (tFromTypeArgs == null || tToTypeArgs == null || tFromTypeArgs.Length != 1 || tToTypeArgs.Length != 1)
{
return null;
}
var tFrom = tFromTypeArgs[0];
var tTo = tToTypeArgs[0];
if (tFrom == tTo && (tFrom.IsValueType || mappingConfig.GetRootMappingOperation(tFrom, tTo).ShallowCopy))
{
return new CustomConverterDescriptor
{
ConversionMethodName = "Convert",
ConverterImplementation = typeof(GenericIEnumerableConverter_OneTypes<>),
ConverterClassTypeArguments = new[] { tFrom }
};
}
return new CustomConverterDescriptor
{
ConversionMethodName = "Convert",
ConverterImplementation = typeof(GenericIEnumerableConverter_DifferentTypes<,>),
ConverterClassTypeArguments = new[] { tFrom, tTo }
};
}
}
class GenericIEnumerableConverter_DifferentTypes<TFrom, TTo> : ICustomConverter
{
private Func<TFrom, TTo> _converter;
public IEnumerable<TTo> Convert(IEnumerable<TFrom> from, object state)
{
if (from == null)
{
return null;
}
TTo[] result = new TTo[from.Count()];
int idx = 0;
foreach (var f in from)
{
result[idx++] = _converter(f);
}
return result;
}
public void Initialize(Type from, Type to, MapConfigBaseImpl mappingConfig)
{
var staticConverters = mappingConfig.GetStaticConvertersManager() ?? StaticConvertersManager.DefaultInstance;
var staticConverterMethod = staticConverters.GetStaticConverter(typeof(TFrom), typeof(TTo));
if (staticConverterMethod != null)
{
_converter = (Func<TFrom, TTo>)Delegate.CreateDelegate(
typeof(Func<TFrom, TTo>),
null,
staticConverterMethod
);
}
else
{
_subMapper = ObjectMapperManager.DefaultInstance.GetMapperImpl(typeof(TFrom), typeof(TTo), mappingConfig);
_converter = ConverterBySubmapper;
}
}
ObjectsMapperBaseImpl _subMapper;
private TTo ConverterBySubmapper(TFrom from)
{
return (TTo)_subMapper.Map(from);
}
}
class GenericIEnumerableConverter_OneTypes<T>
{
public IEnumerable<T> Convert(IEnumerable<T> from, object state)
{
if (from == null)
{
return null;
}
return from;
}
}
This code is just a copy with a minimum of adaptation as possible and can be applyed to objects with many levels of hierarchy.
You can use the above code with the following command:
new DefaultMapConfig().ConvertGeneric(
typeof(IEnumerable<>),
typeof(IEnumerable<>),
new GenericIEnumerableConverterProvider());
This saved my day and I hope to save yours too! hehehe