public class UserModel
{
    public int Id { get; set; }
 
    [Required(ErrorMessage = "(*)")]
    [Display(Name = "نام")]
    [StringLength(maximumLength: 10, MinimumLength = 3, ErrorMessage = "نام باید حداقل 3 و حداکثر 10 حرف باشد")]
    public string FirstName { get; set; }
 
    [Required(ErrorMessage = "(*)")]
    [Display(Name = "نام خانوادگی")]
    [StringLength(maximumLength: 10, MinimumLength = 3, ErrorMessage = "نام خانوادگی باید حداقل 3 و حداکثر 10 حرف باشد")]
    public string LastName { get; set; }
}

public class UserViewModel
{
      public string FirstName { get; set; }
      public string LastName { get; set; }
}

public class MappedMetadataProvider : DataAnnotationsModelMetadataProvider
{
    private readonly IConfigurationProvider _mapper;
 
    public MappedMetadataProvider(IConfigurationProvider mapper)
    {
        _mapper = mapper;
    }
 
    protected override ModelMetadata CreateMetadata(
        IEnumerable<Attribute> attributes,
        Type containerType,
        Func<object> modelAccessor,
        Type modelType,
        string propertyName)
    {
        var mappedAttributes =
            containerType == null ?
            attributes :
            _mapper.GetMappedAttributes(containerType, propertyName, attributes.ToList());
        return base.CreateMetadata(mappedAttributes, containerType, modelAccessor, modelType, propertyName);
    }
}

public class MappedValidatorProvider : DataAnnotationsModelValidatorProvider
{
    private readonly IConfigurationProvider _mapper;
 
    public MappedValidatorProvider(IConfigurationProvider mapper)
    {
        _mapper = mapper;
    }
 
    protected override IEnumerable<ModelValidator> GetValidators(
        ModelMetadata metadata,
        ControllerContext context,
        IEnumerable<Attribute> attributes)
    {
 
        var mappedAttributes =
            metadata.ContainerType == null ?
            attributes :
            _mapper.GetMappedAttributes(metadata.ContainerType, metadata.PropertyName, attributes.ToList());
        return base.GetValidators(metadata, context, mappedAttributes);
    }
}

public static class AutoMapperExtensions
{
    public static IEnumerable<Attribute> GetMappedAttributes(
        this IConfigurationProvider mapper,
        Type viewModelType,
        string viewModelPropertyName,
        IList<Attribute> existingAttributes)
    {
        if (viewModelType != null)
        {
            foreach (var typeMap in mapper.GetAllTypeMaps().Where(i => i.DestinationType == viewModelType))
            {
                var propertyMaps = typeMap.GetPropertyMaps()
                    .Where(propertyMap => !propertyMap.IsIgnored() && propertyMap.SourceMember != null)
                    .Where(propertyMap => propertyMap.DestinationProperty.Name == viewModelPropertyName);
 
                foreach (var propertyMap in propertyMaps)
                {
                    foreach (Attribute attribute in propertyMap.SourceMember.GetCustomAttributes(true))
                    {
                        if (existingAttributes.All(i => i.GetType() != attribute.GetType()))
                        {
                            yield return attribute;
                        }
                    }
                }
            }
        }
 
        if (existingAttributes == null)
        {
            yield break;
        }
 
        foreach (var attribute in existingAttributes)
        {
            yield return attribute;
        }
    }
}

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    WebApiConfig.Register(GlobalConfiguration.Configuration);
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes); 
 
    Mappings.RegisterMappings();
    ModelMetadataProviders.Current = new MappedMetadataProvider(Mapper.Engine.ConfigurationProvider);
 
    var modelValidatorProvider = ModelValidatorProviders.Providers
        .Single(provider => provider is DataAnnotationsModelValidatorProvider);
    ModelValidatorProviders.Providers.Remove(modelValidatorProvider);
    ModelValidatorProviders.Providers.Add(new MappedValidatorProvider(Mapper.Engine.ConfigurationProvider));
}

public class HomeController : Controller
{
    public ActionResult Index()
    {
        var model = new UserModel { FirstName = "و", Id = 1, LastName = "ن" };
        var viewModel = Mapper.Map<UserViewModel>(model);
        return View(viewModel);
    }
 
    [HttpPost]
    public ActionResult Index(UserViewModel data)
    {
        return View(data);
    }
}

@model Sample12.ViewModels.UserViewModel
 
@using (Html.BeginForm("Index", "Home", FormMethod.Post, htmlAttributes: new { @class = "form-horizontal", role = "form" }))
{
    <div class="row">
        <div class="form-group">
            @Html.LabelFor(d => d.FirstName, htmlAttributes: new { @class = "col-md-2 control-label" })
            <div class="col-md-10">
                @Html.TextBoxFor(d => d.FirstName)
                @Html.ValidationMessageFor(d => d.FirstName)
            </div>
        </div>
        <div class="form-group">
            @Html.LabelFor(d => d.LastName, htmlAttributes: new { @class = "col-md-2 control-label" })
            <div class="col-md-10">
                @Html.TextBoxFor(d => d.LastName)
                @Html.ValidationMessageFor(d => d.LastName)
            </div>
        </div>
        <div class="form-group">
            <div class="col-md-offset-2 col-md-10">
                <input type="submit" value="ارسال" class="btn btn-default" />
            </div>
        </div>
    </div>
}

@if (HotelRoomModel.HotelRoomImages.Count > 0)
{
    var serial = 1;
    foreach (var roomImage in HotelRoomModel.HotelRoomImages)
    {
        <div class="col-md-2 mt-3">
            <div class="room-image" style="background: url('@roomImage.RoomImageUrl') 50% 50%; ">
                <span class="room-image-title">@serial</span>
            </div>
            <button type="button"
                    @onclick="()=>DeletePhoto(roomImage)"
                    class="btn btn-outline-danger btn-block mt-4">Delete</button>
        </div>
        serial++;
    }
}

@code
{
    private const string UploadFolder = "Uploads";

    private void DeletePhoto(HotelRoomImageDTO imageDto)
    {
        var imageFileName = imageDto.RoomImageUrl.Replace($"{UploadFolder}/", "", StringComparison.OrdinalIgnoreCase);
        if (HotelRoomModel.Id == 0 && Title == "Create")
        {
            FileUploadService.DeleteFile(imageFileName, WebHostEnvironment.WebRootPath, UploadFolder);
            HotelRoomModel.HotelRoomImages.Remove(imageDto);
        }
    }
}

@code
{
    private List<string> DeletedImageFileNames = new List<string>();

    private void DeletePhoto(HotelRoomImageDTO imageDto)
    {
        var imageFileName = imageDto.RoomImageUrl.Replace($"{UploadFolder}/", "", StringComparison.OrdinalIgnoreCase);
        if (HotelRoomModel.Id == 0 && Title == "Create")
        {
            // ...              
        }
        else
        {
            // Edit Mode
            DeletedImageFileNames.Add(imageFileName);
            HotelRoomModel.HotelRoomImages.Remove(imageDto); // Update UI
        }
    }

    private async Task HandleHotelRoomUpsert()
    {
        // ...
 
        if (HotelRoomModel.Id != 0 && Title == "Update")
        {
            // Update Mode
            var updatedRoomDto = await HotelRoomService.UpdateHotelRoomAsync(HotelRoomModel.Id, HotelRoomModel);

            foreach(var imageFileName in DeletedImageFileNames)
            {
                FileUploadService.DeleteFile(imageFileName, WebHostEnvironment.WebRootPath, UploadFolder);
            }

            // await AddHotelRoomImageAsync(updatedRoomDto);
            await JsRuntime.ToastrSuccess($"The `{HotelRoomModel.Name}` updated successfully.");
        }
        else
        {
           // ... 
        }
    }
}

.spinner {
  border: 16px solid silver !important;
  border-top: 16px solid #337ab7 !important;
  border-radius: 50% !important;
  width: 80px !important;
  height: 80px !important;
  animation: spin 700ms linear infinite !important;
  top: 50% !important;
  left: 50% !important;
  transform: translate(-50%, -50%);
  position: absolute !important;
}

@keyframes spin {
  0% {
    transform: rotate(0deg);
  }

  100% {
    transform: rotate(360deg);
  }
}

@code
{
    private bool IsImageUploadProcessStarted;

    private async Task HandleImageUpload(InputFileChangeEventArgs args)
    {
        try
        {
            IsImageUploadProcessStarted = true;
            // ...
        }
        finally
        {
            IsImageUploadProcessStarted = false;
        }
    }
}

<InputFile OnChange="HandleImageUpload" multiple></InputFile>
<div class="row">
@if (IsImageUploadProcessStarted)
{
    <div class="col-md-12">
        <span><i class="spinner"></i> Please wait.. Images are uploading...</span>
    </div>
}

@using BlazorServer.App.Pages.Components

<Confirmation @ref="Confirmation1"
    OnCancel="OnCancelDeleteImageClicked"
    OnConfirm="@(()=>OnConfirmDeleteImageClicked(ImageToBeDeleted))">
    <div>
        Do you want to delete @ImageToBeDeleted?.RoomImageUrl image?
    </div>
</Confirmation>

    private Confirmation Confirmation1;
    private HotelRoomImageDTO ImageToBeDeleted;

    private void OnCancelDeleteImageClicked()
    {
        // Confirmation1.Hide();
    }

    private void DeletePhoto(HotelRoomImageDTO imageDto)
    {
        ImageToBeDeleted = imageDto;
        Confirmation1.Show();
    }

    private void OnConfirmDeleteImageClicked(HotelRoomImageDTO imageDto)
    {

<td>
    <NavLink href="@($"hotel-room/edit/{room.Id}")" class="btn btn-primary">Edit</NavLink>
    <button class="btn btn-danger" @onclick="()=>HandleDeleteRoom(room)">Delete</button>
</td>

<Confirmation @ref="Confirmation1"
    OnCancel="OnCancelDeleteRoomClicked"
    OnConfirm="OnConfirmDeleteRoomClicked">
    <div>
        Do you want to delete @RoomToBeDeleted?.Name?
    </div>
</Confirmation>

@code
{
    private List<HotelRoomDTO> HotelRooms = new List<HotelRoomDTO>();
    private HotelRoomDTO RoomToBeDeleted;
    private Confirmation Confirmation1;

    private void OnCancelDeleteRoomClicked()
    {
        // Confirmation1.Hide();
    }

    private void HandleDeleteRoom(HotelRoomDTO roomDto)
    {
        RoomToBeDeleted = roomDto;
        Confirmation1.Show();
    }

    private async Task OnConfirmDeleteRoomClicked()
    {
        if(RoomToBeDeleted is null)
        {
            return;
        }

        await HotelRoomService.DeleteHotelRoomAsync(RoomToBeDeleted.Id);
        HotelRooms.Remove(RoomToBeDeleted); // Update UI
    }

An exception occurred while iterating over the results of a query for context type 'BlazorServer.DataAccess.ApplicationDbContext'.
System.InvalidOperationException: A second operation was started on this context before a previous operation completed.
This is usually caused by different threads concurrently using the same instance of DbContext.
For more information on how to avoid threading issues with DbContext, see https://go.microsoft.com/fwlink/?linkid=2097913.

public class CustomStringModelBinderProvider : IModelBinderProvider
{
    public IModelBinder GetBinder(ModelBinderProviderContext context)
    {
        if (context == null)
        {
            throw new ArgumentNullException(nameof(context));
        }
 
        if (context.Metadata.IsComplexType)
        {
            return null;
        }
 
        var fallbackBinder = new SimpleTypeModelBinder(context.Metadata.ModelType);
        if (context.Metadata.ModelType == typeof(string))
        {
            return new CustomStringModelBinder(fallbackBinder);
        }
        return fallbackBinder;
    }
}

public class CustomStringModelBinder : IModelBinder
{
    private readonly IModelBinder _fallbackBinder;
    public CustomStringModelBinder(IModelBinder fallbackBinder)
    {
        if (fallbackBinder == null)
        {
            throw new ArgumentNullException(nameof(fallbackBinder));
        }
        _fallbackBinder = fallbackBinder;
    }
 
    public Task BindModelAsync(ModelBindingContext bindingContext)
    {
        if (bindingContext == null)
        {
            throw new ArgumentNullException(nameof(bindingContext));
        }
 
        var valueProviderResult = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
        if (valueProviderResult != ValueProviderResult.None)
        {
            bindingContext.ModelState.SetModelValue(bindingContext.ModelName, valueProviderResult);
 
            var valueAsString = valueProviderResult.FirstValue;
            if (string.IsNullOrWhiteSpace(valueAsString))
            {
                return _fallbackBinder.BindModelAsync(bindingContext);
            }
 
            var model = valueAsString.Replace((char)1610, (char)1740).Replace((char)1603, (char)1705);
            bindingContext.Result = ModelBindingResult.Success(model);
            return Task.CompletedTask;
        }
 
        return _fallbackBinder.BindModelAsync(bindingContext);
    }
}

public static class CustomStringModelBinderExtensions
{
    public static MvcOptions UseCustomStringModelBinder(this MvcOptions options)
    {
        if (options == null)
        {
            throw new ArgumentNullException(nameof(options));
        }
 
        var simpleTypeModelBinder = options.ModelBinderProviders.FirstOrDefault(x => x.GetType() == typeof(SimpleTypeModelBinderProvider));
        if (simpleTypeModelBinder == null)
        {
            return options;
        }
 
        var simpleTypeModelBinderIndex = options.ModelBinderProviders.IndexOf(simpleTypeModelBinder);
        options.ModelBinderProviders.Insert(simpleTypeModelBinderIndex, new CustomStringModelBinderProvider());
        return options;
    }
}

public void ConfigureServices(IServiceCollection services)
{
    services.AddMvc(options =>
    {
        options.UseCustomStringModelBinder(); 
    });

 >ng g m UploadFile -m app.module --routing

 >ng g c UploadFile/UploadFileSimple

 >ng g cl UploadFile/Ticket

export class Ticket {
  constructor(public description: string = "") {}
}

import { Ticket } from "./../ticket";

export class UploadFileSimpleComponent implements OnInit {
  model = new Ticket();

<div class="container">
  <h3>Support Form</h3>
  <form #form="ngForm" (submit)="submitForm(form)" novalidate>
    <div class="form-group" [class.has-error]="description.invalid && description.touched">
      <label class="control-label">Description</label>
      <input #description="ngModel" required type="text" class="form-control"
        name="description" [(ngModel)]="model.description">
      <div *ngIf="description.invalid && description.touched">
        <div class="alert alert-danger"  *ngIf="description.errors.required">
          description is required.
        </div>
      </div>
    </div>

    <div class="form-group">
      <label class="control-label">Screenshot(s)</label>
      <input #screenshotInput required type="file" multiple (change)="fileChange($event)"
        class="form-control" name="screenshot">
    </div>

    <button class="btn btn-primary" [disabled]="form.invalid" type="submit">Ok</button>
  </form>
</div>

 (change)="fileChange($event)"

fileChange(event) {
    const filesList: FileList = event.target.files;
    console.log("fileChange() -> filesList", filesList);
}

 C:\Program Files (x86)\Microsoft VS Code\resources\app\extensions\node_modules\typescript\lib\lib.dom.d.ts

{
    "lib": [
      "es2016",
      "dom"
    ]
  }
}

import { Component, OnInit, ViewChild, ElementRef } from "@angular/core";

export class UploadFileSimpleComponent implements OnInit {
  @ViewChild("screenshotInput") screenshotInput: ElementRef;

  submitForm(form: NgForm) {
    const fileInput: HTMLInputElement = this.screenshotInput.nativeElement;
    console.log("fileInput.files", fileInput.files);
  }

 >ng g s UploadFile/UploadFileSimple -m upload-file.module

import { Http, RequestOptions, Response, Headers } from "@angular/http";
import { Injectable } from "@angular/core";
import { Observable } from "rxjs/Observable";
import "rxjs/add/operator/do";
import "rxjs/add/operator/catch";
import "rxjs/add/observable/throw";
import "rxjs/add/operator/map";
import "rxjs/add/observable/of";

import { Ticket } from "./ticket";

@Injectable()
export class UploadFileSimpleService {
  private baseUrl = "api/SimpleUpload";

  constructor(private http: Http) {}

  private extractData(res: Response) {
    const body = res.json();
    return body || {};
  }

  private handleError(error: Response): Observable<any> {
    console.error("observable error: ", error);
    return Observable.throw(error.statusText);
  }

  postTicket(ticket: Ticket, filesList: FileList): Observable<any> {
    if (!filesList || filesList.length === 0) {
      return Observable.throw("Please select a file.");
    }

    const formData: FormData = new FormData();

    for (const key in ticket) {
      if (ticket.hasOwnProperty(key)) {
        formData.append(key, ticket[key]);
      }
    }

    for (let i = 0; i < filesList.length; i++) {
      formData.append(filesList[i].name, filesList[i]);
    }

    const headers = new Headers();
    headers.append("Accept", "application/json");
    const options = new RequestOptions({ headers: headers });

    return this.http
      .post(`${this.baseUrl}/SaveTicket`, formData, options)
      .map(this.extractData)
      .catch(this.handleError);
  }
}

  postTicket(ticket: Ticket, filesList: FileList): Observable<any> {
    const formData: FormData = new FormData();

    for (const key in ticket) {
      if (ticket.hasOwnProperty(key)) {
        formData.append(key, ticket[key]);
      }
    }

    for (let i = 0; i < filesList.length; i++) {
      formData.append(filesList[i].name, filesList[i]);
    }

    const headers = new Headers();
    headers.append("Accept", "application/json");
    const options = new RequestOptions({ headers: headers });

    return this.http
      .post(`${this.baseUrl}/SaveTicket`, formData, options)
      .map(this.extractData)
      .catch(this.handleError);

import { UploadFileSimpleService } from "./../upload-file-simple.service";

export class UploadFileSimpleComponent implements OnInit {
  constructor(private uploadService: UploadFileSimpleService  ) {}

  submitForm(form: NgForm) {
    const fileInput: HTMLInputElement = this.screenshotInput.nativeElement;
    console.log("fileInput.files", fileInput.files);

    this.uploadService
      .postTicket(this.model, fileInput.files)
      .subscribe(data => {
        console.log("success: ", data);
      });
  }

namespace AngularTemplateDrivenFormsLab.Models
{
    public class Ticket
    {
        public int Id { set; get; }
        public string Description { set; get; }
    }
}

using System.IO;
using System.Threading.Tasks;
using AngularTemplateDrivenFormsLab.Models;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Mvc;

namespace AngularTemplateDrivenFormsLab.Controllers
{
    [Route("api/[controller]")]
    public class SimpleUploadController : Controller
    {
        private readonly IHostingEnvironment _environment;
        public SimpleUploadController(IHostingEnvironment environment)
        {
            _environment = environment;
        }

        [HttpPost("[action]")]
        public async Task<IActionResult> SaveTicket(Ticket ticket)
        {
            //TODO: save the ticket ... get id
            ticket.Id = 1001;

            var uploadsRootFolder = Path.Combine(_environment.WebRootPath, "uploads");
            if (!Directory.Exists(uploadsRootFolder))
            {
                Directory.CreateDirectory(uploadsRootFolder);
            }

            var files = Request.Form.Files;
            foreach (var file in files)
            {
                //TODO: do security checks ...!

                if (file == null || file.Length == 0)
                {
                    continue;
                }

                var filePath = Path.Combine(uploadsRootFolder, file.FileName);
                using (var fileStream = new FileStream(filePath, FileMode.Create))
                {
                    await file.CopyToAsync(fileStream).ConfigureAwait(false);
                }
            }

            return Created("", ticket);
        }
    }
}

 SaveTicket(Ticket ticket)

 formData.append(filesList[i].name, filesList[i]);

var files = Request.Form.Files;
foreach (var file in files)