I'm discovering ASP.NET Core MVC and I'm on my first project. Creating a cool web shop.
I'm currently wondering how to implement faulty information checking for example in the controller
Let's say there a product page, whenever users clicks on a product they will hit the function below.
As you can see the function accepts an int parameter named id, it will search in the database for the id that fits the productId, but I'm wondering how do I add error checking here? Like for example if the id does not exist in database return to page XX?
Also feel free to give suggestions to the function if you don't like it.
I've already tried to do a simple if and else statement
if(productvm == null)
{
then
return RedirectToPage("Index")
}
else
return View("ProductPage", productVm);
but it didn't seem to hit the if statement
[Route("ProductPage/{id}")]
public IActionResult ProductPage(int id)
{
Product product = _uow.Products.SelectProduct(id);
var stockViewModels = new List<StockViewModel>();
foreach (Stock stock in product.Stock)
{
stockViewModels.Add(new StockViewModel()
{
Id = stock.Id,
Description = stock.Description,
IsAvailable = stock.IsAvailable,
Quantity = stock.Quantity,
});
}
ProductViewModel productVm = new ProductViewModel
{
Name = product.Name,
Id = product.Id,
Description = product.Description,
Price = product.Price,
Stocks = stockViewModels,
};
if (productVm == null)
{
return RedirectToPage("Productslist");
}
else
{
return View("ProductPage", productVm);
}
}
I basically want an error handling the controller if the id is not found in the database then execute XX
The way how I test the function is to change the ID when browsing the page with an ID that does not exist in the database, then I get this error:
https://i.imgur.com/1amWx43.png
and I want to handle it
I think your problem is that you have new the productVm object before the if, so it will never be null, for your case, you should get check the product object and not the productVm, for example:
Product product = _uow.Products.SelectProduct(id);
if (product == null)
{
return RedirectToPage("Productslist");
}
else
{
return View("ProductPage", productVm);
}
I'm working on a dotnet mvc5 application. Here's a function from my api of customer controller
public IHttpActionResult GetCustomers()
{
var customerDtos = _context.Customers.ToList().Select(Mapper.Map<Customer, CustomerDto>);
return Ok(customerDtos);
}
I need to add "TYPEAHEAD" plugin to my application. The video series/instructor I'm following says to make the function code change to
public IHttpActionResult GetCustomers(string query = null)
{
var customersQuery = _context.Customers
.Include(c => c.MembershipType);
if (!String.IsNullOrWhiteSpace(query))
customersQuery = customersQuery.Where(c => c.Name.Contains(query));
var customerDtos = customersQuery
.ToList()
.Select(Mapper.Map<Customer, CustomerDto>);
return Ok(customerDtos);
}
in order to make "TypeAhead" plug in work on my view.
The only problem is previously while creating customers I didn't feel the need to add "MembershipType" class to my customer. So how do I use the new code without MembershipType. Is there any other attribute I can replace it with? Name, ID etc.
.Include(c => c.MembershipType);
essentially means that you also want to include the 'child' collection of MembershipType
See here for more information on Loading Related Entities
For your case, you can simply omit this.
public IHttpActionResult GetCustomers(string query = null)
{
var customersQuery = _context.Customers;
if (!String.IsNullOrWhiteSpace(query))
customersQuery = customersQuery.Where(c => c.Name.Contains(query));
var customerDtos = customersQuery
.ToList()
.Select(Mapper.Map<Customer, CustomerDto>);
return Ok(customerDtos);
}
You don't need to replace it with anything.
customersQuery is then an IQueryable<Customer> which the rest of this code can append Where clause to.
It is not executed against the database until the ToList call.
Currently I am doing like this:
For Example:
public update(Person model)
{
// Here model is model return from form on post
var oldobj = db.Person.where(x=>x.ID = model.ID).SingleOrDefault();
db.Entry(oldobj).CurrentValues.SetValues(model);
}
It works, but for example,
I have 50 columns in my table but I displayed only 25 fields in my form (I need to partially update my table, with remaining 25 column retain same old value)
I know it can be achieve by "mapping columns one by one" or by creating "hidden fields for those remaining 25 columns".
Just wondering is there any elegant way to do this with less effort and optimal performance?
This is a very good question. By default I have found that as long as change tracking is enabled (it is by default unless you turn it off), Entity Framework will do a good job of applying to the database only what you ask it to change.
So if you only change 1 field against the object and then call SaveChanges(), EF will only update that 1 field when you call SaveChanges().
The problem here is that when you map a view model into an entity object, all of the values get overwritten. Here is my way of handling this:
In this example, you have a single entity called Person:
Person
======
Id - int
FirstName - varchar
Surname - varchar
Dob - smalldatetime
Now let's say we want to create a view model which will only update Dob, and leave all other fields exactly how they are, here is how I do that.
First, create a view model:
public class PersonDobVm
{
public int Id { get; set; }
public DateTime Dob { get; set; }
public void MapToModel(Person p)
{
p.Dob = Dob;
}
}
Now write the code roughly as follows (you'll have to alter it to match your context name etc):
DataContext db = new DataContext();
Person p = db.People.FirstOrDefault();
// you would have this posted in, but we are creating it here just for illustration
var vm = new PersonDobVm
{
Id = p.Id, // the Id you want to update
Dob = new DateTime(2015, 1, 1) // the new DOB for that row
};
vm.MapToModel(p);
db.SaveChanges();
The MapToModel method could be even more complicated and do all kinds of additional checks before assigning the view model fields to the entity object.
Anyway, the result when SaveChanges is called is the following SQL:
exec sp_executesql N'UPDATE [dbo].[Person]
SET [Dob] = #0
WHERE ([Id] = #1)
',N'#0 datetime2(7),#1 int',#0='2015-01-01 00:00:00',#1=1
So you can clearly see, Entity Framework has not attempted to update any other fields - just the Dob field.
I know in your example you want to avoid coding each assignment by hand, but I think this is the best way. You tuck it all away in your VM so it does not litter your main code, and this way you can cater for specific needs (i.e. composite types in there, data validation, etc). The other option is to use an AutoMapper, but I do not think they are safe. If you use an AutoMapper and spelt "Dob" as "Doob" in your VM, it would not map "Doob" to "Dob", nor would it tell you about it! It would fail silently, the user would think everything was ok, but the change would not be saved.
Whereas if you spelt "Dob" as "Doob" in your VM, the compiler will alert you that the MapToModel() is referencing "Dob" but you only have a property in your VM called "Doob".
I hope this helps you.
I swear by EntityFramework.Extended. Nuget Link
It lets you write:
db.Person
.Where(x => x.ID == model.ID)
.Update(p => new Person()
{
Name = newName,
EditCount = p.EditCount+1
});
Which is very clearly translated into SQL.
Please try this way
public update(Person model)
{
// Here model is model return from form on post
var oldobj = db.Person.where(x=>x.ID = model.ID).SingleOrDefault();
// Newly Inserted Code
var UpdatedObj = (Person) Entity.CheckUpdateObject(oldobj, model);
db.Entry(oldobj).CurrentValues.SetValues(UpdatedObj);
}
public static object CheckUpdateObject(object originalObj, object updateObj)
{
foreach (var property in updateObj.GetType().GetProperties())
{
if (property.GetValue(updateObj, null) == null)
{
property.SetValue(updateObj,originalObj.GetType().GetProperty(property.Name)
.GetValue(originalObj, null));
}
}
return updateObj;
}
I have solved my Issue by using FormCollection to list out used element in form, and only change those columns in database.
I have provided my code sample below; Great if it can help someone else
// Here
// collection = FormCollection from Post
// model = View Model for Person
var result = db.Person.Where(x => x.ID == model.ID).SingleOrDefault();
if (result != null)
{
List<string> formcollist = new List<string>();
foreach (var key in collection.ToArray<string>())
{
// Here apply your filter code to remove system properties if any
formcollist.Add(key);
}
foreach (var prop in result.GetType().GetProperties())
{
if( formcollist.Contains(prop.Name))
{
prop.SetValue(result, model.GetType().GetProperty(prop.Name).GetValue(model, null));
}
}
db.SaveChanges();
}
I still didn't find a nice solution for my problem, so I created a work around. When loading the Entity, I directly make a copy of it and name it entityInit. When saving the Entity, I compare the both to see, what really was changed. All the unchanged Properties, I set to unchanged and fill them with the Database-Values. This was necessary for my Entities without Tracking:
// load entity without tracking
var entityWithoutTracking = Context.Person.AsNoTracking().FirstOrDefault(x => x.ID == _entity.ID);
var entityInit = CopyEntity(entityWithoutTracking);
// do business logic and change entity
entityWithoutTracking.surname = newValue;
// for saving, find entity in context
var entity = Context.Person.FirstOrDefault(x => x.ID == _entity.ID);
var entry = Context.Entry(entity);
entry.CurrentValues.SetValues(entityWithoutTracking);
entry.State = EntityState.Modified;
// get List of all changed properties (in my case these are all existing properties, including those which shouldn't have changed)
var changedPropertiesList = entry.CurrentValues.PropertyNames.Where(x => entry.Property(x).IsModified).ToList();
foreach (var checkProperty in changedPropertiesList)
{
try
{
var p1 = entityWithoutTracking.GetType().GetProperty(checkProperty).GetValue(entityWithoutTracking);
var p2 = entityInit.GetType().GetProperty(checkProperty).GetValue(entityInit);
if ((p1 == null && p2 == null) || p1.Equals(p2))
{
entry.Property(checkProperty).CurrentValue = entry.Property(checkProperty).OriginalValue; // restore DB-Value
entry.Property(checkProperty).IsModified = false; // throws Exception for Primary Keys
}
} catch(Exception) { }
}
Context.SaveChanges(); // only surname will be updated
This is way I did it, assuming the new object has more columns to update that the one we want to keep.
if (theClass.ClassId == 0)
{
theClass.CreatedOn = DateTime.Now;
context.theClasses.Add(theClass);
}
else {
var currentClass = context.theClasses.Where(c => c.ClassId == theClass.ClassId)
.Select(c => new TheClasses {
CreatedOn = c.CreatedOn
// Add here others fields you want to keep as the original record
}).FirstOrDefault();
theClass.CreatedOn = currentClass.CreatedOn;
// The new class will replace the current, all fields
context.theClasses.Add(theClass);
context.Entry(theClass).State = EntityState.Modified;
}
context.SaveChanges();
In EF you can do like this
var result = db.Person.Where(x => x.ID == model.ID).FirstOrDefault();
if(result != null){
result.Name = newName;
result.DOB = newDOB;
db.Person.Update(result);
}
Or you can use
using (var db= new MyDbContext())
{
var result= db.Person.Where(x => x.ID == model.ID).FirstOrDefault();
result.Name= newName;
result.DOB = newDOB;
db.Update(result);
db.SaveChanges();
}
For more detail please EntityFramework Core - Update Only One Field
No Worry guys
Just write raw sql query
db.Database.ExecuteSqlCommand("Update Person set Name='"+_entity.Name+"' where Id = " + _entity.ID + "");
I am trying to select all usernames in MVC membership provider into a queryable list to plug into a function that checks if a given username exists and modifies it by adding a number at the end if it is so. I am struggling to get the list. I am not sure if what I am trying to achieve is achievable.
So far this is what I have come up with as below
var allusers = (from MembershipUser u in Membership.GetAllUsers()
select new
{
Uname = u.UserName
}).ToList();
But It does not work and gives the error
cannot convert from 'System.Collections.Generic.List<AnonymousType#1>' to 'System.Collections.Generic.List<string>'
I have realised that the error goes away only when the below code is in place.
private string GetUniqueSlug(string Uname, object allusers)
{
throw new NotImplementedException();
}
But this is the function that is supposed to be evaluated
//unique username for autogenerate
private string GetUniqueSlug(string Uname, List<string> allusers)
{
var slug = Uname.ToSeoUrl();
return allusers.Any(s => s == slug)? GetUniqueSlugInternal(slug, allusers) : slug;
}
When the condition is triggered to generate a new uname, the not implemented step gets the focus
It worked with this instead
List<string> allusers = (from MembershipUser c in Membership.GetAllUsers()
select new { UserName = c.ToString() }).Select(t=>t.UserName).ToList();
I want to get:
list of ApplicationUsers who are in role "NormalUser" to anybody
list of all ApplicationUsers only to Admins only.
I did this:
// GET: ApplicationUsers
public ActionResult Index() {
// if you are Admin you will get all users
if (User.IsInRole("Admin"))
return View(db.Users.ToList());
//if you are somebody else(not Admin) you will see only list of NormalUsers
//HERE I GET ERROR
var list = db.Users.Where(x => UserManager.IsInRole(x.Id, "NormalUser")).ToList(); // here I get error
return View(list);
}
UserManager inside code above is: UserManager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(db));
But unfortunately my LINQ expresiion is incorrect. I get error:
LINQ to Entities does not recognize the method 'Boolean IsInRole[ApplicationUser,String](Microsoft.AspNet.Identity.UserManager`2[WebApplication2.Models.ApplicationUser,System.String], System.String, System.String)' method, and this method cannot be translated into a store expression.
Question: How to correctly get list of users who are in role "NormalUser"?
The UserManager.IsInRole function isn't supported at the database, but if your application can bear the weight of pulling the whole User table back from the database before applying your filter then you can just add a ToList between your Users table reference and your Where filter, i.e.
var list = db.Users.ToList().Where(x => UserManager.IsInRole(x.Id, "NormalUser")).ToList();
I reached here for a good quick answer but could not find one. So decided to put on what I got for any other visitor who comes here. To get the List of Users in any particular Role, one can use this code.
public async Task<ActionResult> Index()
{
List<ApplicationUser> appUsers=new List<ApplicationUser>();
await Task.Run( () =>
{
var roleManager = new RoleManager<IdentityRole>( new RoleStore<IdentityRole>( db ) );
var adminRole=roleManager.FindByName("Admin");
appUsers = db.Users.Where( x => x.Roles.Any( s => s.RoleId == adminRole.Id ) ).ToList();
} );
return View( appUsers );
}
It would be useful to know how Roles and Application users relate.
If the user can only belong to one role, it would be fine for you to do something like this:
var list = db.Users.ToList().Where(x => x.Role == "NormalUser").ToList();
Id the user can be part of multiple roles, it would look something more like this:
var list = db.Users.ToList().Where(x => x.Roles.Contains("NormalUser")).ToList();
Hope this helps.