I have the following viewModel:
namespace Flashcard.Models
{
public class CreateCardViewModel
{
[HiddenInput(DisplayValue = false)]
public int SetId { get; set; }
[Required]
public ICollection<Side> Sides { get; set; }
}
}
I use this ViewModel against the Card Controller:
public class CardController : Controller
{
//
// GET: /Card/
public ActionResult Create(int setId)
{
var model = new CreateCardViewModel();
var side = new Side() {Content = "Blank Side"};
model.SetId = setId;
model.Sides.Add(side);
return View(model);
}
}
However when I call the Create action, I get a nullReferenceException because model.Sides is null, which does not seem to be the same as empty. I believe I created an empty ICollection Sides in the ViewModel - why is it null in the controller?
For some context - a Card can have one or several Sides. I'm trying to always add a Side whenever a Card is created.
you need to initiate a Collection and assign it to the property of your object as follows:
public class CardController : Controller
{
//
// GET: /Card/
public ActionResult Create(int setId)
{
var model = new CreateCardViewModel();
var side = new Side() {Content = "Blank Side"};
model.SetId = setId;
model.Sides = new List<Side>();
model.Sides.Add(side);
return View(model);
}
}
Your collection is null. make one and assign to your prop.
Related
I am currently using <ObjectGraphDataAnnotationsValidator/> to validate complex models.
So far so good, except that there is also a requirement to check against the database to see if a record with the same value already exists.
I have tried implementing the <CustomValidator/> as per advised in https://learn.microsoft.com/en-us/aspnet/core/blazor/forms-validation?view=aspnetcore-5.0#validator-components
However, it seems to only work for the top level properties.
And the <ObjectGraphDataAnnotationsValidator/> does not work with remote validations (or does it!?)
So say that I have:
*Parent.cs*
public int ID {get;set;}
public List<Child> Children {get;set;}
*Child.cs*
public int ID {get;set;}
public int ParentID {get;set}
public string Code {get;set;}
<EditForm Model="#Parent">
.
.
.
Child.Code has a unique constraint in the database.
I want to warn users "This 'Code' already exists! Please try entering a different value.", so that no exceptions will be thrown.
For now, I am a bit lost as to where my next step is.
In the past with asp.net core mvc, I could achieve this using remote validations.
Is there an equivalent to remote validations in blazor?
If not, what should I do to achieve the same result, to remotely validate the sub properties for complex models?
Any advises would be appreciated. Thanks!
[Updated after #rdmptn's suggestion 2021/01/24]
ValidationMessageStore.Add() accepts the struct FieldIdentifier, meaning that I can simply add a overload of the CustomValidator.DisplayErrors to make it work:
public void DisplayErrors(Dictionary<FieldIdentifier, List<string>> errors)
{
foreach (var err in errors)
{
messageStore.Add(err.Key, err.Value);
}
CurrentEditContext.NotifyValidationStateChanged();
}
Full example below:
#using Microsoft.AspNetCore.Components.Forms
#using System.ComponentModel.DataAnnotations
#using System.Collections.Generic
<EditForm Model="parent" OnSubmit="Submit">
<ObjectGraphDataAnnotationsValidator></ObjectGraphDataAnnotationsValidator>
<CustomValidator #ref="customValidator"></CustomValidator>
<ValidationSummary></ValidationSummary>
#if (parent.Children != null)
{
#foreach (var item in parent.Children)
{
<div class="form-group">
<label>Summary</label>
<InputText #bind-Value="item.Code" class="form-control"></InputText>
</div>
}
}
<input type="submit" value="Submit" class="form-control"/>
</EditForm>
#code{
private CustomValidator customValidator;
private Parent parent;
public class Parent
{
public int Id { get; set; }
[ValidateComplexType]
public List<Child> Children { get; set; }
}
public class Child
{
public int Id { get; set; }
public int ParentId { get; set; }
public string Code { get; set; }
}
protected override void OnInitialized()
{
parent = new Parent()
{
Id = 1,
Children = new List<Child>()
{
new Child()
{
Id = 1,
ParentId = 1,
Code = "A"
},
new Child()
{
Id = 1,
ParentId = 1,
Code = "B"
}
}
};
}
public void Submit()
{
customValidator.ClearErrors();
var errors = new Dictionary<FieldIdentifier, List<string>>();
//In real operations, set this when you get data from your db
List<string> existingCodes = new List<string>()
{
"A"
};
foreach (var child in parent.Children)
{
if (existingCodes.Contains(child.Code))
{
FieldIdentifier fid = new FieldIdentifier(model: child, fieldName: nameof(Child.Code));
List<string> msgs = new List<string>() { "This code already exists." };
errors.Add(fid, msgs);
}
}
if (errors.Count() > 0)
{
customValidator.DisplayErrors(errors);
}
}
}
The [Remote] validation attribute is tied to MVC and is not usable for Blazor.
ObjectGraphDataAnnotationsValidator is not enough. In addition, each property, that represents an object with possible validation needs to be decorated with a [ValidateComplexType] attribute.
In your CustomValidatior, you can see DI to get your API service to call your API and validate your constraint.
public class Parent
{
...other properties...
[ValidateComplexType]
public List<Child> Children {get; set; }
}
public class Child
{
...other properties...
[Required]
[IsUnique(ErrorMessage = "This 'Code' already exists! Please try entering a different value.")]
public String Code {get; set;}
}
public class IsUniqueAttribute : ValidationAttribute
{
protected override ValidationResult IsValid(object value, ValidationContext validationContext)
{
var service = (IYourApiService)validationContext.GetService(typeof(IYourApiService));
//unfortunately, no await is possible inside the validation
Boolean exists = service.IsUnique((String)value);
if(exists == false)
{
return ValidationResult.Success;
}
return new ValidationResult(ErrorMessage, new[] { validationContext.MemberName });
}
}
You might want to check out FluentValidation as this library provide features for asynchronous validation. I'm not sure if this validator can be used inside Blazor WASM.
I am trying to figure out how to create a second DB context in EF7 RC1. In the past I could use a constructor with :base("connectionName") but that no longer seems an option since it says cannot convert string to System.IServiceProvider.
My second context code is as follows:
public class DecAppContext : DbContext
{
public DecAppContext()
// :base("DefaultConnection")
{
}
public DbSet<VignetteModels> VignetteModels { get; set; }
public DbSet<VignetteResult> Result { get; set; }
}
}
In my config.json I have the connection specified:
"Data": {
"DefaultConnection": {
"ConnectionString": "Server=(localdb)\\mssqllocaldb;Database=aspnet5-xxxxx...;Trusted_Connection=True;MultipleActiveResultSets=true"
}
}
In my configure services section of my startup I have both contexts added:
services.AddEntityFramework()
.AddSqlServer()
.AddDbContext<ApplicationDbContext>(options =>
options.UseSqlServer(Configuration["Data:DefaultConnection:ConnectionString"]))
.AddDbContext<DecAppContext>(options => options.UseSqlServer(Configuration["Data:DefaultConnection:ConnectionString"]));
The applicationDB context works fine since I can create a user and login without issue
However when I try to access the other context as in my controller via:
private DecAppContext db = new DecAppContext();
var vignette = db.VignetteModels.SingleOrDefault(v => v.CaseId == vid);
I get the error:
No database providers are configured. Configure a database provider by
overriding OnConfiguring in your DbContext class or in the
AddDbContext method when setting up services.
Any working examples in EF7 RC1 with multiple db contexts and accessing them would be much appreciated.
First of all I would recommend you the article from the wiki of EntityFramework on GitHub. The article describes many ways to define DbContext, which references to a section of appsettings.json. I personally prefer the way with the usage of [FromServices] attribute.
The code could be about the following:
First of all you defined appsettings.json with the following content
{
"Data": {
"ApplicationDbConnectionString": "Server=(localdb)\\mssqllocaldb;Database=ApplicationDb;Trusted_Connection=True;MultipleActiveResultSets=true",
"DecAppDbConnectionString": "Server=Server=(localdb)\\mssqllocaldb;Database=DecAppDb;Trusted_Connection=True;MultipleActiveResultSets=true"
}
}
where you define two connection strings.
Seconds you declare the classes DecAppContext and ApplicationDbContext which have DbContext as the base class. The simplest form will be just
public class ApplicationDbContext : DbContext
{
}
public class DecAppContext : DbContext
{
}
without any DbSet properties.
Third Step. You use Microsoft.Extensions.DependencyInjection to inject the database contexts. To do this you need just include in Startup.cs something like
public class Startup
{
// property for holding configuration
public IConfigurationRoot Configuration { get; set; }
public Startup(IHostingEnvironment env)
{
// Set up configuration sources.
var builder = new ConfigurationBuilder()
.AddJsonFile("appsettings.json")
.AddEnvironmentVariables();
// save the configuration in Configuration property
Configuration = builder.Build();
}
// This method gets called by the runtime. Use this method to add services to the container.
public void ConfigureServices(IServiceCollection services)
{
// Add framework services.
services.AddMvc()
.AddJsonOptions(options => {
options.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
});
services.AddEntityFramework()
.AddSqlServer()
.AddDbContext<ApplicationDbContext>(options => {
options.UseSqlServer(Configuration["Data:ApplicationDbConnectionString"]);
})
.AddDbContext<DecAppContext>(options => {
options.UseSqlServer(Configuration["Data:DecAppDbConnectionString"]);
});
}
public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
{
...
}
}
Se create two DbContext (DecAppContext and ApplicationDbContext) using the configuration "Data:DecAppDbConnectionString" and "Data:ApplicationDbConnectionString".
Now we can just use the context in the controller. For example
[Route("api/[controller]")]
public class UsersController : Controller
{
[FromServices]
public ApplicationDbContext ApplicationDbContext { get; set; }
[FromServices]
public DecAppContext DecAppContext { get; set; }
[HttpGet]
public IEnumerable<object> Get() {
var returnObject = new List<dynamic>();
using (var cmd = ApplicationDbContext.Database.GetDbConnection().CreateCommand()) {
cmd.CommandText = "SELECT Id, FirstName FROM dbo.Users";
if (cmd.Connection.State != ConnectionState.Open)
cmd.Connection.Open();
var retObject = new List<dynamic>();
using (var dataReader = cmd.ExecuteReader())
{
while (dataReader.Read())
{
var dataRow = new ExpandoObject() as IDictionary<string, object>;
for (var iFiled = 0; iFiled < dataReader.FieldCount; iFiled++)
dataRow.Add(
dataReader.GetName(iFiled),
dataReader.IsDBNull(iFiled) ? null : dataReader[iFiled] // use null instead of {}
);
retObject.Add((ExpandoObject)dataRow);
}
}
return retObject;
}
}
}
or the same using async/await:
[Route("api/[controller]")]
public class UsersController : Controller
{
[FromServices]
public ApplicationDbContext ApplicationDbContext { get; set; }
[FromServices]
public DecAppContext DecAppContext { get; set; }
[HttpGet]
public async IEnumerable<object> Get() {
var returnObject = new List<dynamic>();
using (var cmd = ApplicationDbContext.Database.GetDbConnection().CreateCommand()) {
cmd.CommandText = "SELECT Id, FirstName FROM dbo.Users";
if (cmd.Connection.State != ConnectionState.Open)
cmd.Connection.Open();
var retObject = new List<dynamic>();
using (var dataReader = await cmd.ExecuteReaderAsync())
{
while (await dataReader.ReadAsync())
{
var dataRow = new ExpandoObject() as IDictionary<string, object>;
for (var iFiled = 0; iFiled < dataReader.FieldCount; iFiled++)
dataRow.Add(dataReader.GetName(iFiled), dataReader[iFiled]);
retObject.Add((ExpandoObject)dataRow);
}
}
return retObject;
}
}
}
One can just declare the property public ApplicationDbContext ApplicationDbContext { get; set; } with the attribute [FromServices] and ASP.NET initialize it from the context injected in ConfigureServices. In the same way one can use the second context DecAppContext whenever you need it.
The above code example will execute SELECT Id, FirstName From dbo.Users in the database context and return JSON data in the form [{"id":123, "firstName":"Oleg"},{"id":456, "firstName":"Xaxum"}]. The conversion of property names from Id and FirstName to id and firstName will be done automatically during serialization because of usage AddJsonOptions in ConfigureServices.
UPDATE: I have to reference the announcement. The next version of MVC (RC2) will require to change the above code to use [FromServices] as additional parameter (of method Get() for example) instead of usage public property [FromServices] public ApplicationDbContext ApplicationDbContext { get; set; }. One will need to remove the property ApplicationDbContext and to add additional parameter to Get() method: public async IEnumerable<object> Get([FromServices] ApplicationDbContext applicationDbContext) {...}. Such changes can be easy done. See here and example of the changes in the demo example of MVC:
[Route("api/[controller]")]
public class UsersController : Controller
{
[HttpGet]
public async IEnumerable<object> Get(
[FromServices] ApplicationDbContext applicationDbContext,
[FromServices] DecAppContext decAppContext)
{
var returnObject = new List<dynamic>();
// ... the same code as before, but using applicationDbContext
// and decAppContext parameters instead of ApplicationDbContext
// and DecAppContext properties
}
I've got class named PagedList which looks like this:
public class PagedList<T> : List<T>
{
public int PageIndex { get; private set; }
public int PageSize { get; private set; }
public int TotalCount { get; private set; }
public int TotalPages { get; private set; }
public bool HasPrevious
{
get
{
return (this.PageIndex > 0);
}
}
public bool HasNext
{
get
{
return (this.PageIndex + 1 < this.TotalPages);
}
}
public PagedList(IEnumerable<T> source, int pageIndex, int pageSize)
{
this.PageIndex = pageIndex;
this.PageSize = pageSize;
this.TotalCount = source.Count();
this.TotalPages = (int)Math.Ceiling(TotalCount / (double)PageSize);
this.AddRange(source.Skip(this.PageIndex * this.PageSize).Take(this.PageSize));
}
}
In my Customers controller I use it like so:
public ActionResult Index(int? page)
{
IRepository<UserInfo> profile = ObjectFactory.GetInstance<IRepository<UserInfo>>();
const int pageSize = 25;
IQueryable<UserInfo> profiles = profile.GetAll().OrderBy(x => x.LastName).AsQueryable<UserInfo>();
var pagedCustomers = new PagedList<UserInfo>(profiles, page ?? 0, pageSize);
return View(pagedCustomers);
}
And finally in my Index.cshtml file I set up my Model like so:
#model System.Web.Mvc.ViewPage<PagedList<Clusteris.Data.UserInfo>>
And When I go Model. it's a huge list, nothing to do with the PagedList I created in the Customers controller.
Anyone got any ideas on what I'm doing wrong?
UPDATE:
Screenshot:
PagedList is enumerable. To access individual UserInfo object use #foreach(var userInfo in Model)
Someone else mentioned about the use of IQueryable. It's a good practice to use ToArray() or ToList() at boundaries. Your repository is a boundary, so I would consider moving the paging logic to it and make it return either the PagedList object or the data necessary to construct one.
Your model class right now is System.Web.Mvc.ViewPage<PagedList<Clusteris.Data.UserInfo>> as opposed to PagedList<Clusteris.Data.UserInfo> - this is likely why you are seeing all of this strange data on your model.
System.Web.Mvc.ViewPage is a component used to render models and shouldn't be the model itself. Change your model type to just PagedList<Clusteris.Data.UserInfo> and it should work.
While in search of trying to implement unique key validations for my db using EF CodeFirst/Mvc3 I came upon this post http://blogs.msdn.com/b/adonet/archive/2011/05/27/ef-4-1-validation.aspx which gave an example on how to do it by using IValidateObject for my object model:
public class Category : IValidatableObject
{
public int CategoryID { get; set; }
public string CategoryName { get; set; }
public string Description { get; set; }
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
var testContext = (TestContext)validationContext.Items["Context"];
if (testContext.Categories.Any(
c => c.CategoryName == CategoryName && c.CategoryID != CategoryID))
{
yield return new ValidationResult("A category with the same name already exists!", new[] { "CategoryName" });
}
yield break;
}
}
and overriding DbEntityValidationResult ValidateEntity:
public class TestContext : DbContext
{
public DbSet<Test.Models.Category> Categories { get; set; }
protected override DbEntityValidationResult ValidateEntity( DbEntityEntry entityEntry, IDictionary<object, object> items)
{
var myItems = new Dictionary<object, object>();
myItems.Add("Context", this);
return base.ValidateEntity(entityEntry, myItems);
}
}
And the action on the controller
[HttpPost]
public ActionResult Create(Category category)
{
if (ModelState.IsValid) {
categoryRepository.InsertOrUpdate(category);
categoryRepository.Save();
return RedirectToAction("Index");
} else {
return View();
}
}
But I get the error: "The given key was not present in the dictionary." for the line
var testContext = (TestContext)validationContext.Items["Context"];
It seems like Validate on the object is getting called which accesses "Context" before its set in the override ValidateEntity code.
At first I thought it could have been ModelState.Isvalid triggering validate too early but it wasn't.
Anyone know what I'm missing here or what I'm doing wrong? Thanks in advance.
Model.IsValid definitely triggers it too early and perhaps something else. IValidatableObject is global interface used by both MVC and EF but your method in DbContext is called only when you call SaveChanges on the context so any usage of IValidatableObject prior to calling SaveChanges will result in the exception. You must use another approach if you want to validate your entity this way. For example store context in HttpContext.Items - you can create custom action filter and instantiate and store the context before the operation call and dispose it after operation call - hopefully it will cover all problems.
I was facing the same problem... Then after a lot of Googling I finally found this:
Exercise 3: Using IValidatableObject Custom Validation
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
MusicStoreEntities storeDB = new MusicStoreEntities();
if (storeDB.Albums.Any(
a => a.Title.Trim().ToUpper() == this.Title.Trim().ToUpper() &&
a.ArtistId == (int)this.ArtistId))
{
yield return new ValidationResult("Existing Album", new string[] { "Title" });
}
}
As you see in their example, they instantiate a new Context and as such there's no need for validationContext.Items["Context"];. Doing so we won't get this error anymore.
I am creating a fluent HtmlHelper in MVC - to create a grid based on HTML.
I am aware of mvc contrib and WebGrid - but I am making my own and have a specific problem:
I have to enter this:
#Html.DSGridFor().AddColumn(x=>x.FirstOrDefault().Message)
but I want to be able to type this:
#Html.DSGridFor().AddColumn(x=>x.Message)
The code that gets called when I start with #Html.DSGridFor() - taking in the page based model.
public static DSGridHelper<TModel> DSGridFor<TModel>(this HtmlHelper<TModel> html)
{
return new DSGridHelper<TModel>(html);
}
and then within the class DSGridHelper I have this:
public DSGridHelper<TModel> AddColumn(Expression<Func<TModel, dynamic>> property, string HeaderText = null)
{
string ColumnName = (property.Body as MemberExpression).Member.Name;
DSGridColumn DSGC = new DSGridColumn();
DSGC.ColumnName = ColumnName;
DSGC.HeaderText = HeaderText ?? ColumnName;
DSColumnList.Add(DSGC);
return this;
}
public List<DSGridColumn> DSColumnList { get; set; }
and the column class at the moment is really basic:
public class DSGridColumn
{
public DSGridColumn()
{
}
public string ColumnName { get; set; }
public string HeaderText { get; set; }
}
I can get this code working fine with string based column names, but I want the declaring code in the razor page to be simple in format and strongly typed. At the moment I have to type x=>x.First().Message but I really only need x=>x.Message to identify the column.
I appreciate any help.
UPDATE
Thanks to Justin I can now provide my/our code.
View:
#(Html.DSGridFor3().AddColumn(x => x.Message)
.AddColumn(x => x.Host)
.ToMvcString())
HTML Helper call:
public static DSGridHelper3<T> DSGridFor3<T>(this HtmlHelper<IEnumerable<T>> htmlHelper)
{
return new DSGridHelper3<T>(htmlHelper);
}
Returning class:
public class DSGridHelper3<T>
{
private HtmlHelper _htmlHelper;
//private IEnumerable<T> _dataList;
public List<DSGridColumn> DSColumnList { get; set; }
public DSGridHelper3(HtmlHelper<IEnumerable<T>> htmlHelper)
{
_htmlHelper = htmlHelper;
// _dataList = htmlHelper.ViewData.Model;
DSColumnList = new List<DSGridColumn>();
}
public DSGridHelper3<T> AddColumn(Expression<Func<T, object>> property)
{
string columnName = (property.Body as MemberExpression).Member.Name;
DSGridColumn DSGC = new DSGridColumn();
DSGC.ColumnName = columnName;
DSGC.HeaderText = columnName;
DSColumnList.Add(DSGC);
return this;
}
public MvcHtmlString ToMvcString()
{
sb.Append("<table>");
sb.Append("<tr>");
sb.Append("<td>");
sb.Append("hello world within a table");
sb.Append(#"</td>");
sb.Append("<td>");
sb.Append("hello world within a table");
sb.Append(#"</td>");
sb.Append(#"</tr>");
sb.Append(#"</table>");
return new MvcHtmlString(sb.ToString());
}
}
UPDATE 2
If you wanted to manually insert a different type (perhaps because you are going to get a small amount of table data from ViewData rather than the model of the page) then here is some more code:
View:
#(Html.DSGridFor3<DanSoftware.MVC.Areas.Errors.Code.ELMAH_Error>().AddColumn(x => x.Message).ToMvcString();)
Alternative signature for the DSGridHelper ...helper
public static DSGridHelper3<T> DSGridFor3<T>(this HtmlHelper htmlHelper)
{
return new DSGridHelper3<T>(htmlHelper);
}
Additional constructor:
public DSGridHelper3(HtmlHelper htmlHelper)
{
_htmlHelper = htmlHelper;
// _dataList = htmlHelper.ViewData.Model;
DSColumnList = new List<DSGridColumn>();
}
Hope this helps someone and thanks Justin!
I dont have Visual Studio with me but I'll take a stab at this...
I would take in a collection as a datatype either in your DsGridFor method or in the AddColumn method. This will allow you to send Strongly-typed arguments from a collection. Say you wanted a generic method of AddColumn for a given collection with access to the class properties vs the collection methods, it would look something like this (just an example):
public static DSGridHelper<T> AddColumn<T>(this HtmlHelper<IEnumerable<T>> htmlHelper, Expression<Func<T, object>> property) where T : class
{
string columnName = (property.Body as MemberExpression).Member.Name;
DSGridColumn DSGC = new DSGridColumn();
DSGC.ColumnName = ColumnName;
DSGC.HeaderText = HeaderText ?? ColumnName;
DSColumnList.Add(DSGC);
return this;
}
For your situation, to new-up a DsGridHelper class I might explicitly set a model-type first and then add overloads as I go:
public static DSGridHelper<T> DSGridFor<T>(this HtmlHelper<IEnumerable<T>> htmlHelper) where T : class
{
return new DSGridHelper<T>(htmlHelper);
}
And then my DsGridHelper might look something like this:
public class DsGridHelper<T>
{
private HtmlHelper _htmlHelper;
private IEnumerable<T> _dataList;
public DsGridHelper(HtmlHelper<IEnumerable<T>> htmlHelper)
{
_htmlHelper = htmlHelper;
_dataList = htmlHelper.ViewData.Model;
}
public DsGridHelper<T> AddColumn(Expression<Func<T, object>> property)
{
string columnName = (property.Body as MemberExpression).Member.Name;
DSGridColumn DSGC = new DSGridColumn();
DSGC.ColumnName = ColumnName;
DSGC.HeaderText = HeaderText ?? ColumnName;
DSColumnList.Add(DSGC);
return this;
}
}