在 Razor 页面上使用多个 OnGet 处理程序方法时引发 NullReferenceException [重复]

Question

第一个 OnGet 收集所有数据并使其可用。在这里我也设置了我的属性值，我认为我可以重用它。当我尝试使用 OnGetDownload 或 OnGetView 时出现问题。

OnGet 传递一个id 参数，后面两个传递一个filed 参数。 OnGet id 参数用于设置我的属性public Employee Employee {get; set;}

我遇到的问题是尝试在 OnGetView 或 OnGetDownload 中重用该属性时。 *是的，我的代码需要重构，但我是新手并且正在学习：D

cshtml.cs

    public class IndexModel : PageModel
    {
        private readonly IConfiguration _configuration;
        private readonly ICustomer _customer;
        private readonly UserManager<IdentityUser> _userManager;

        public IndexModel(IConfiguration configuration,
            ICustomer customer, UserManager<IdentityUser> userManager)
        {
            _configuration = configuration;
            _customer = customer;
            _userManager = userManager;
        }
        

        public Employee Employee { get; set; }
        public List<AzureFileModel> AzureFileModel { get; private set; } = new List<AzureFileModel>();

        public async Task OnGetAsync(int id)
        {
            Employee = await _customer.GetEmployeeNo(id);
            var empNo = Employee.EmployeeNumber; // related table

            string fileStorageConnection = _configuration.GetValue<string>("FileStorage");
            CloudStorageAccount storageAccount = CloudStorageAccount.Parse(fileStorageConnection);
            CloudFileShare share = storageAccount.CreateCloudFileClient().GetShareReference("test");
            CloudFileDirectory root = share.GetRootDirectoryReference();
            CloudFileDirectory dir = root.GetDirectoryReference(empNo.EmployeeOnline+"/files");

           // list all files in the directory
           AzureFileModel = await ListSubDir(dir);
        }


public static async Task<List<AzureFileModel>> ListSubDir(CloudFileDirectory fileDirectory)
        {
            var fileData = new List<AzureFileModel>();

            FileContinuationToken token = null;
            do
            {
                FileResultSegment resultSegment = await fileDirectory.ListFilesAndDirectoriesSegmentedAsync(token);
                foreach (var fileItem in resultSegment.Results)
                {
                    if (fileItem is CloudFile)
                    {
                        var cloudFile = (CloudFile) fileItem;
                        //get the cloudfile's properties and metadata
                        await cloudFile.FetchAttributesAsync();

                        // Add properties to FileDataModel 
                        fileData.Add(new AzureFileModel()
                        {
                            FileName = cloudFile.Name,
                            Size = Math.Round((cloudFile.Properties.Length / 1024f), 2).ToString(),
                            DateModified = DateTime.Parse(cloudFile.Properties.LastModified.ToString()).ToLocalTime()
                                .ToString()
                        });
                    }

                    if (fileItem is CloudFileDirectory)
                    {
                        var cloudFileDirectory = (CloudFileDirectory) fileItem;
                        await cloudFileDirectory.FetchAttributesAsync();

                        //list files in the directory
                        var result = await ListSubDir(cloudFileDirectory);
                        fileData.AddRange(result);
                    }

                    // get the FileContinuationToken to check if we need to stop the loop
                    token = resultSegment.ContinuationToken;
                }
            } while (token != null);

            return fileData.OrderByDescending(o => Convert.ToDateTime(o.DateModified)).ToList();

        }

 public async Task<IActionResult> OnGetView(string fileId)
        {
            var empNo = Employee.EmployeeNumber;

            string fileStorageConnection = _configuration.GetValue<string>("FileStorage");
            CloudStorageAccount storageAccount = CloudStorageAccount.Parse(fileStorageConnection);
            CloudFileShare share = storageAccount.CreateCloudFileClient().GetShareReference("test");
            CloudFileDirectory rootDir = share.GetRootDirectoryReference();
            CloudFileDirectory dir = rootDir.GetDirectoryReference(empNo.EmployeeOnline+"/files");
            CloudFile file = dir.GetFileReference(fileId);

            try
            {
                var stream = await file.OpenReadAsync();
                return File(stream, "application/pdf");
            }
            catch (Exception ex)
            {
                throw new Exception(String.Format($"An error occurred while executing the view {ex.Message}"));
            }
            
        }

public async Task<IActionResult> OnGetDownload(string fileId)
        {
            removed for brevity

        }
}

我已经尝试在OnGetView(string fileId, int id) 中传递第二个参数，但同样，我无法检索已登录的用户 ID 来设置它。我错过了什么？

cshtml

@page "{id:int}"
@model NavraePortal.WebApp.Pages.Files.IndexModel
@{
    ViewData["Title"] = "Documents";
}

<h1>Pay Stub Copies</h1>
<table class="table table-bordered">
    <thead>
    <tr>
        <th>File Name</th>
        <th>File Date</th>
        <th>Download</th>
        <th>View</th>
    </tr>
    </thead>
    <tbody>
    @foreach (var data in Model.AzureFileModel)
    {
        <tr>
            <td>@data.FileName</td>
            <td>@data.DateModified</td>
            <td>
                <a class="btn btn-primary" asp-route-fileId="@data.FileName" asp-page-handler="Download">Download</a>
            </td>
            <td>
                <a class="btn btn-info" asp-route-fileId="@data.FileName" asp-page-handler="View">View</a>
            </td>
        </tr>
    }
    </tbody>
</table>

Answer 1

你可以尝试使用TempData，这里有一个demo：

cshtml.cs:

public IActionResult OnGet()
        {
            TempData["EmployeeNumber"] = "111";
            AzureFileModel = new List<AzureFileModel> { new AzureFileModel { FileName = "file1", DateModified = "sss" }, new AzureFileModel { FileName = "file2", DateModified = "ddd" } };
            return Page();
        }
        public async Task<IActionResult> OnGetView(string fileId)
        {
            
            var empNo = TempData.Peek("EmployeeNumber");
            return Page();

        }

        public async Task<IActionResult> OnGetDownload(string fileId)
        {
            var empNo = TempData.Peek("EmployeeNumber");
            return Page();
        
        }

结果：