I am working on a asp.net core 1.1 project and i want to create paging in my some views. I studied microsoft documents about paging in asp core but it is very simple mode with 1 table. In my view i use multi table and use a viewmodel to initialize it. I want to use PagingList<T>.CreateAsync() method to create paging but get error:
can not convert from system.linq.Iqueryable<> to system.linq.IorderedQueryable<>
my action:
[HttpGet]
public async Task<IActionResult> Index(int? page)
{
List<BookListViewModel> model = new List<BookListViewModel>();
var query = (from b in _context.books
join a in _context.authors on b.AuthorID equals a.AuthorId
join bg in _context.bookgroups on b.BookGroupID equals bg.BookGroupId
select new
{
b.BookId,
b.BookName,
b.BookPageCount,
b.BookImage,
b.AuthorID,
b.BookGroupID,
a.AuthorName,
bg.BookGroupName
});
foreach (var item in query)
{
BookListViewModel objmodel = new BookListViewModel();
objmodel.BookId = item.BookId;
objmodel.BookName = item.BookName;
objmodel.BookImage = item.BookImage;
objmodel.BookPageCount = item.BookPageCount;
objmodel.AuthorId = item.AuthorID;
objmodel.BookGroupId = item.BookGroupID;
objmodel.AuthorName = item.AuthorName;
objmodel.BookGroupName = item.BookGroupName;
model.Add(objmodel);
}
ViewBag.RootPath = "/upload/thumbnailimage/";
int pageSize = 3;
int pageNumber = (page ?? 1);
return View(await PagingList<BookListViewModel>.CreateAsync(model.AsQueryable() , pageNumber, pageSize));
}
I have not yet written anything about paging in index view and it is a simple list of viewmodel
Well can't really be sure from the code you posted. But the exception says the the CreateAsync method needs IOrderedQueryable, but you're giving it an IQueryable.
Try changing it to pass in the query object (which I guess should implement the IOrderedQueryable, if you're using Entity framework).
The idea behind the PagingList (presumably) is to use it to do the paging in the database.
What you're doing is bringing the filterted set into memory (when for-eaching through the result), and then doing doing the paging.
The code might look something like this:
[HttpGet]
public async Task<IActionResult> Index(int page = 1)
{
var query = (from b in _context.books
join a in _context.authors on b.AuthorID equals a.AuthorId
join bg in _context.bookgroups on b.BookGroupID equals bg.BookGroupId
select new BookListViewModel()
{
BookId = b.BookId,
BookName = b.BookName,
BookPageCount = b.BookPageCount,
BookImage = b.BookImage,
AuthorId = b.AuthorID,
BookGroupId = b.BookGroupID,
AuthorName = a.AuthorName,
BookGroupName = bg.BookGroupName
}).AsNoTracking().OrderBy(u => u.BookId);
ViewBag.RootPath = "/upload/thumbnailimage/";
var pagedResult = await PagingList<BookListViewModel>.CreateAsync(query, 10, page);
return View(pagedResult);
}
Hope it helps.
Related
I'm trying to update two entities at the same time but the change is not applying and I think that when I try to return the update entity it doesn't even found it.
Here is my Razor view:
public IActionResult OnPost()
{
if (!ModelState.IsValid)
{
return Page();
}
repositorioFamiliar.Actualizar(Familiar);
return RedirectToPage("/Familiares/DetalleFamiliar", new { IdPaciente = Familiar.IdPaciente });
}
Here is my update function:
public FamiliaresPer Actualizar(FamiliaresPer familiar)
{
var familiarActualizar = (from f in _context.Familiars.Where(p => p.IdFamiliar == familiar.IdFamiliar) select f).FirstOrDefault();
if (familiarActualizar != null)
{
familiarActualizar.Correo = familiar.Correo;
_context.Update(familiarActualizar);
_context.SaveChanges();
}
var personaActualizar = (from p in _context.Personas.Where(p => p.Id == familiar.IdPersona) select p).FirstOrDefault();
if (personaActualizar != null)
{
personaActualizar.Telefono = familiar.Telefono;
_context.Update(personaActualizar);
_context.SaveChanges();
}
var familiares = from p in _context.Familiars
from p1 in _context.Personas
where p.IdPaciente == familiar.IdPaciente
where p.IdPersona == p1.IdPersona
select new FamiliaresPer()
{
IdFamiliar = p.IdFamiliar,
IdPaciente = p.IdPaciente,
IdPersona = p1.IdPersona,
Id = p1.Id,
Nombres = p1.Nombres,
Apellidos = p1.Apellidos,
Genero = p1.Genero,
Telefono = p1.Telefono,
Parentesco = p.Parentesco,
Correo = p.Correo,
};
FamiliaresPer familiaresPer = familiares.FirstOrDefault();
return familiaresPer;
}
When I submit the form I get an error
NullReferenceException: Object reference not set to an instance of an object
And the link shows the IdPaciente = 0 when it should use the same IdPaciente of the updated entity (which the Id never changes).
In your OnPost( ) Action Method, you used repositorioFamiliar.Actualizar(Familiar);
but it looks like you didn't define 'Familiar'.
In addition, when I look at your code. I can give you an advice. Let's say your first update was done correctly and you got an error in the second update case. But you want both to be updated at the same time. Assume that the first object is updated in the database but the second one isn't. This is a problem, right? Unit of Work design pattern is very useful to solve this.
In brief, The approach should be to do SaveChanges() after both update processes are completed so there will be no changes in the database until both updates are completed.
I need to write this SQL statement in Entity Framework:
SELECT
SALARIE.MATRICULE, LIEU, UO, UO_RATTACHEMENT,
PHOTO.PHOTO, SALARIE.NOM, SALARIE.PRENOM
FROM
SALARIE, UNITE_ORG, PHOTO
WHERE
SALARIE.LIEU = UNITE_ORG.UO
I use this method for reading my data :
public JsonResult Read()
{
var nodes = entities.UNITE_ORG.Select(p => new NodeModel { id = p.UO, pid = p.UO_RATTACHEMENT, poste = p.POSTE, img=p.LIB_COMPLET, Fullname=p.RESPONSABLE });
return Json(new { nodes = nodes }, JsonRequestBehavior.AllowGet);
}
I need to change this declaration of nodes.
Thank you
I believe that the equivalent Entity Framework would be the following:
var result = (from s in context.SALARIE
from u in context.UNITE_ORG
from p in context.PHOTO
where s.LIEU == u.UO
select new {
MATRICULE = s.MATRICULE,
LIEU = s.LIEU,
UO = u.UO,
UO_RATTACHEMENT = UO_RATTACHEMENT, // I don't know where this is coming from
PHOTO = p.PHOTO,
NOM = s.NOM,
PRENOM = s.PRENOM
}
);
However, this is just a guess from the information you have giving.
Also, like I have stated in my comment, I really think you should stop using the syntax for cross joins that you are doing (the , seperated syntax)
// Hi everyone
i do this call in Action :
[HttpGet]
public virtual ActionResult JsonGetProvinces(int countryId)
{
//WebSiteContext WbContext = new WebSiteContext();
//UnitOfWork UnitofWork = new UnitOfWork(WbContext);
var provinces =
(
from province in unitofWork.ProvinceRepository.All
where province.CountryId == countryId
select new
{
Id = province.Id,
Name = province.GetType().GetProperty("Name_" + CultureManager.GetCurrentCultureShortName()).GetValue(province)
}
).ToList();
return Json(provinces, JsonRequestBehavior.AllowGet);
}
something is wrong with my query :
var provinces =
(
from province in unitofWork.ProvinceRepository.All
where province.CountryId == countryId
select new
{
Id = province.Id,
Name = province.GetType().GetProperty("Name_" + CultureManager.GetCurrentCultureShortName()).GetValue(province)
}
).ToList();
Particulary,
Name = province.GetType().GetProperty("Name_" + CultureManager.GetCurrentCultureShortName()).GetValue(province)
In BDD, there is Name_fr, Name_en columns
and i'm trying to take one dynamically... Is it possible ?
Of course, i can take both and choose dynamically the column in View but i would to know how do...
Thank you for your help
The short answer is you need to change your code a bit and using expression tree inside. Look at this question
EF can not translate function calls to SQL. Using expression trees can be comlicated see this question
Here is a sample with expression trees. The GetQuery2 is the same as GetQuery but with expression tree and a propertyname parameter.
public static IQueryable<Foo> GetQuery(BlogContext context)
{
var query = from x in context.BlogEntries
select new Foo
{
NameX = x.Name
};
return query;
}
public static IQueryable<Foo> GetQuery2(BlogContext context, string propertyName)
{
ConstructorInfo ci = typeof(Foo).GetConstructor(new Type[0]);
MethodInfo miFooGetName = typeof(Foo).GetMethod("set_NameX");
MethodInfo miBlogEntry = typeof(BlogEntry).GetMethod("get_" + propertyName);
ParameterExpression param = Expression.Parameter(typeof(BlogEntry), "x");
IQueryable<Foo> result = Queryable.Select<BlogEntry, Foo>(
context.BlogEntries,
Expression.Lambda<Func<BlogEntry, Foo>>(
Expression.MemberInit(
Expression.New(ci, new Expression[0]),
new MemberBinding[]{
Expression.Bind(miFooGetName,
Expression.Property(param,
miBlogEntry))}
),
param
)
);
return result;
}
It is easier the fetch all all language strings and write an additional Property Name that does the magic.
I'm trying to select all the rows out of a database using entity framework for manipulation before they're sent to the form
var ptx = [modelname].[tablename]();
ptx.[tablename].Select(????)
what goes in the ????
I used the entitydatasource and it provide everything I needed for what I wanted to do.
_repository.[tablename].ToList();
Entity Framework has one beautiful thing for it, like :
var users = context.Users;
This will select all rows in Table User, then you can use your .ToList() etc.
For newbies to Entity Framework, it is like :
PortalEntities context = new PortalEntities();
var users = context.Users;
This will select all rows in Table User
How about:
using (ModelName context = new ModelName())
{
var ptx = (from r in context.TableName select r);
}
ModelName is the class auto-generated by the designer, which inherits from ObjectContext.
You can use this code to select all rows :
C# :
var allStudents = [modelname].[tablename].Select(x => x).ToList();
You can simply iterate through the DbSet context.tablename
foreach(var row in context.tablename)
Console.WriteLn(row.field);
or to evaluate immediately into your own list
var allRows = context.tablename.ToList();
If it's under a async method then use ToListAsync()
public async Task<List<DocumentTypes>> GetAllDocumentTypes()
{
var documentTypes = await _context.DocumentTypes.ToListAsync();
return documentTypes;
}
Old post I know, but using Select(x => x) can be useful to split the EF Core (or even just Linq) expression up into a query builder.
This is handy for adding dynamic conditions.
For example:
public async Task<User> GetUser(Guid userId, string userGroup, bool noTracking = false)
{
IQueryable<User> queryable = _context.Users.Select(x => x);
if(!string.IsNullOrEmpty(userGroup))
queryable = queryable.Where(x => x.UserGroup == userGroup);
if(noTracking)
queryable = queryable.AsNoTracking();
return await queryable.FirstOrDefaultAsync(x => x.userId == userId);
}
Here is a few ways to do it (Just assume I'm using Dependency Injection for the DbConext)
public class Example
{
private readonly DbContext Context;
public Example(DbContext context)
{
Context = context;
}
public DbSetSampleOne[] DbSamples { get; set; }
public void ExampleMethod DoSomething()
{
// Example 1: This will select everything from the entity you want to select
DbSamples = Context.DbSetSampleOne.ToArray();
// Example 2: If you want to apply some filtering use the following example
DbSamples = Context.DbSetSampleOne.ToArray().Where(p => p.Field.Equals("some filter"))
}
You can use:
ptx.[tablename].Select( o => true)
The following query is working successfully.
var tabs = (
from r in db.TabMasters
orderby r.colID
select new { r.colID, r.FirstName, r.LastName })
.Skip(rows * (page - 1)).Take(rows);
Now I want to return JsonResult as like
var jsonData = new
{
total = (int)Math.Ceiling((float)totalRecords / (float)rows),
page = page,
records = totalRecords,
rows = (from r in tabs
select new { id = r.colID, cell = new string[] { r.FirstName, r.LastName } }).ToArray()
};
return Json(jsonData, JsonRequestBehavior.AllowGet);
But it will gives me an error like:
The array type 'System.String[]' cannot be initialized in a query result. Consider using 'System.Collections.Generic.List`1[System.String]' instead.
What should I do to get expected result?
I suspect that it's as simple as pushing the last part into an in-process query using AsEnumerable():
var jsonData = new
{
total = (int)Math.Ceiling((float)totalRecords / (float)rows),
page = page,
records = totalRecords,
rows = (from r in tabs.AsEnumerable()
select new { id = r.colID,
cell = new[] { r.FirstName, r.LastName } }
).ToArray()
};
return Json(jsonData, JsonRequestBehavior.AllowGet);
You may want to pull that query out of the anonymous type initializer, for clarity:
var rows = tabs.AsEnumerable()
.Select(r => new { id = r.colID,
cell = new[] { r.FirstName, r.LastName })
.ToArray();
var jsonData = new {
total = (int)Math.Ceiling((float)totalRecords / (float)rows),
page,
records = totalRecords,
rows
};
It's because it's adding to the LINQ query that is your tabs IQueryable. That is then trying to turn the LINQ expression into a SQL query and the provider doesn't support projecting arrays.
You can either change the assignment of the tabs variable's LINQ expression to use ToList to materialize the DB results right then and there, or you can add .AsEnumerable() to the LINQ expression assigned to the rows field of the anonymous type that is your JsonResult. AsEnumerable will demote the IQueryable to an IEnumerable which will prevent your second LINQ query from trying to be added to the DB query and just make it a LINQ-to-objects call like it needs to be.