ASP.NET Core教程【三】实体字段属性、链接标签、并发数据异常、文件上传及读取

实体字段属性

    public class Movie
    {
        public int ID { get; set; }
        public string Title { get; set; }

        [Display(Name = "Release Date")]
        [DataType(DataType.Date)]
        public DateTime ReleaseDate { get; set; }
        public string Genre { get; set; }
        public decimal Price { get; set; }
    }

<label asp-for="Movie.Title" class="control-label"></label>

[StringLength(60, MinimumLength = 3)]
[Required]
[Range(1, 100)]
[RegularExpression(@"^[A-Z]+[a-zA-Z''-'\s]*$")]
[DataType(DataType.Currency)]

[DisplayFormat(DataFormatString = "{0:yyyy-MM-dd}"]

[RegularExpression(@"^[A-Z]+[a-zA-Z''-'\s]*$"), Required, StringLength(30)]

链接标签

<a asp-page="./Edit" asp-route-id="@item.ID">Edit</a> 
<a asp-page="./Details" asp-route-id="@item.ID">Details</a>
<a asp-page="./Delete" asp-route-id="@item.ID">Delete</a>

@page "{id:int?}"

@page "{searchString?}"

并发数据异常

public async Task<IActionResult> OnPostAsync()
{
    if (!ModelState.IsValid)
    {
        return Page();
    }

    _context.Attach(Movie).State = EntityState.Modified;

    try
    {
        await _context.SaveChangesAsync();
    }
    catch (DbUpdateConcurrencyException)
    {
        if (!_context.Movie.Any(e => e.ID == Movie.ID))
        {
            return NotFound();
        }
        else
        {
            throw;
        }
    }

    return RedirectToPage("./Index");
}

文件上传及读取

<div class="form-group">
  <label asp-for="FileUpload.UploadPublicSchedule" class="control-label"></label>
  <input asp-for="FileUpload.UploadPublicSchedule" type="file" class="form-control" style="height:auto" />
  <span asp-validation-for="FileUpload.UploadPublicSchedule" class="text-danger"></span>
</div>

using Microsoft.AspNetCore.Http;
using System.ComponentModel.DataAnnotations;

namespace RazorPagesMovie.Models
{
    public class FileUpload
    {
        [Required]
        [Display(Name="Title")]
        [StringLength(60, MinimumLength = 3)]
        public string Title { get; set; }

        [Required]
        [Display(Name="Public Schedule")]
        public IFormFile UploadPublicSchedule { get; set; }
    }
}

public static async Task<string> ProcessFormFile(IFormFile formFile, ModelStateDictionary modelState)
{
            var fieldDisplayName = string.Empty;
            // 通过反射拿到实例的字段，再拿到字段的DisplayAttribute
            MemberInfo property = typeof(FileUpload).GetProperty(formFile.Name.Substring(formFile.Name.IndexOf(".") + 1));
            if (property != null)
            {
                var displayAttribute = property.GetCustomAttribute(typeof(DisplayAttribute)) as DisplayAttribute;
                if (displayAttribute != null)
                {
                    fieldDisplayName = $"{displayAttribute.Name} ";
                }
            }
            // 通过Path.GetFileName拿到文件名
            var fileName = WebUtility.HtmlEncode(Path.GetFileName(formFile.FileName));
            if (formFile.ContentType.ToLower() != "text/plain")
            {
                modelState.AddModelError(formFile.Name, $"The {fieldDisplayName}file ({fileName}) must be a text file.");
            }
            // 判断文件长度
            if (formFile.Length == 0)
            {
                modelState.AddModelError(formFile.Name, $"The {fieldDisplayName}file ({fileName}) is empty.");
            }
            else
            {
                try
                {
                    string fileContents;
                    using (var reader = new StreamReader(formFile.OpenReadStream(), new UTF8Encoding(encoderShouldEmitUTF8Identifier: false, throwOnInvalidBytes: true), detectEncodingFromByteOrderMarks: true))
                    {
                        fileContents = await reader.ReadToEndAsync();
                        // 再验证一遍文件内容的长度，以防文件只有一个BOM头
                        if (fileContents.Length > 0)
                        {
                            return fileContents;
                        }
                        else
                        {
                            modelState.AddModelError(formFile.Name, $"The {fieldDisplayName}file ({fileName}) is empty.");
                        }
                    }
                }
                catch (IOException ex)
                {
                    modelState.AddModelError(formFile.Name, $"The {fieldDisplayName}file ({fileName}) upload failed. Please contact the Help Desk for support.");
                }
            }

            return string.Empty;
}

var publicScheduleData = await FileHelpers.ProcessFormFile(FileUpload.UploadPublicSchedule, ModelState);