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我们正在使用 SAS 密钥从我们的 Azure 服务器访问文件。使用 ASP.NET 控制器检索链接并使用 HTML 元素显示。

我们第一次请求链接时，图像完美显示。第二次请求图像（例如页面刷新）时，它们没有显示 - 控制台状态 403 未找到图像文件。如果我们将 HTML 元素中的链接复制到新的浏览器选项卡中，则会显示图像。

有没有人有这个问题的经验？

谢谢。

控制器

    // GET: /<controller>/edit
    public async Task<IActionResult> Edit(int id)
    {

        Checklist checklist = await AM.Checklist.FindAsync(id);

        if (checklist == null)
        {
            return StatusCode(404);
        }

        ChecklistViewModel cVM = new ChecklistViewModel(checklist);

        cVM.productPartNum = (await AM.Product.FindAsync(checklist.productNum)).partId;
        cVM.checklistTypesDropdown = await cVM.GetChecklistOptions(AM);
        List<Field> fields = await AM.Field.Where(x => x.checklistId == checklist.id).OrderBy(x=>x.section).ThenBy(x=>x.order).ToListAsync();




        //connect to the file storate account
        CloudStorageAccount storageAccount = CloudStorageAccount.Parse(CloudConfigurationManager.GetSetting("StorageConnectionString"));

        // Create a CloudFileClient object for credentialed access to File storage.
        CloudFileClient fileClient = storageAccount.CreateCloudFileClient();

        // Get a reference to the file share
        CloudFileShare share = fileClient.GetShareReference("newfileshare");


        string policyName = "sampleSharePolicy" + DateTime.UtcNow.Ticks;
        CloudFileDirectory rootDir = null;
        CloudFileDirectory fileDir = null;

        // Ensure that the share exists.
        if (share.Exists())
        {


            // Create a new shared access policy and define its constraints.
            SharedAccessFilePolicy sharedPolicy = new SharedAccessFilePolicy()
            {
                SharedAccessStartTime = DateTime.UtcNow.AddMinutes(-5),
                SharedAccessExpiryTime = DateTime.UtcNow.AddHours(8),
                Permissions = SharedAccessFilePermissions.Read | SharedAccessFilePermissions.Write
            };

            // Get existing permissions for the share.
            FileSharePermissions permissions = await share.GetPermissionsAsync();

            //Check length of SharedAccessPolicies
            if (permissions.SharedAccessPolicies.Count >= 5)
            {
                permissions.SharedAccessPolicies.Remove(permissions.SharedAccessPolicies.Keys.First());
            }

            // Add the shared access policy to the share's policies. Note that each policy must have a unique name.
            permissions.SharedAccessPolicies.Add(policyName, sharedPolicy);
            await share.SetPermissionsAsync(permissions);

            // Generate a SAS for a file in the share and associate this access policy with it.
            rootDir = share.GetRootDirectoryReference();
        }



        cVM.changeHappened = new List<bool>();

        cVM.Fields = new List<FieldViewModel>();
        int i = 0;
        foreach(Field f in fields)
        {
            FieldViewModel newFVM = new FieldViewModel(f);

            cVM.changeHappened.Add(false);

            if (f.attachmentReq && f.attachmentData != null)
            {

                //changeHappened will keep track of what images have been changed in order to avoid resubmitting same images
                cVM.changeHappened.Add(false);



                if (f.attachmentType.Contains("image"))
                {
                    fileDir = rootDir.GetDirectoryReference("Images");
                }
                else
                {
                    fileDir = rootDir.GetDirectoryReference("files");
                }

                CloudFile file = fileDir.GetFileReference(f.attachmentData);
                string sasToken = file.GetSharedAccessSignature(null, policyName);
                string tick = $"&{ DateTimeOffset.UtcNow.Ticks}";
                Uri fileSasUri = new Uri(file.StorageUri.PrimaryUri.ToString() + sasToken + tick);

                newFVM.link = fileSasUri.AbsoluteUri;

                //// Create a new CloudFile object from the SAS, and write some text to the file.
                //CloudFile fileSas = new CloudFile(fileSasUri);
                //fileSas.UploadText("This write operation is authenticated via SAS.");
                //Console.WriteLine(fileSas.DownloadText());
            }



            if (newFVM.textReq)
            {
                newFVM.fieldDropdownOptions = await newFVM.getDropdownOptions(AM);
            }

            cVM.Fields.Add(newFVM);
        }

        return View(cVM);
    }

显示图像的 div

                                        <div class="col-sm-5">


                                            @if (Model.Fields[i].attachmentData != null)
                                            {
                                                @if (Model.Fields[i].attachmentType.Contains("image/"))
                                                {

                                                    <img src="@Model.Fields[i].link" id="image_@i" height="50" width="50" align="middle"/>
                                                    <a hidden="hidden" id="link_@i"></a>
                                                }
                                                else
                                                {
                                                    <img hidden="hidden" id="image_@i" height="50" width="50" align="middle"/>
                                                    <a id="link_@i">@Model.Fields[i].attachmentData</a>
                                                }

                                            }
                                            else
                                            {
                                                <img hidden="hidden" id="image_@i" height="50" width="50" align="middle"/>
                                                <a hidden="hidden" id="link_@i"></a>
                                            }

                                        </div>
4

1 回答 1

1

根据您的描述和代码，我已经重现了该问题。

我猜您面临 403 错误的原因是您的 MVC 代码在文件存储已经设置并启用权限的 SharedAccessPolicies 之前向文件存储发送请求。

所以它会返回 403 禁止错误，说你的 SAS 令牌没用。

另外，我不建议你每次都添加 SharedAccessPolicies，因为如果有 6 个人同时访问你的网站，第一个人的 SharedAccessPolicies 可能会被删除。所以第一个人无法获得文件图像。

我建议你可以只使用一个 SharedAccessPolicies。

您可以每次重置 SharedAccessFilePolicy 的 SharedAccessExpiryTime。

更多细节，你可以参考下面的代码示例：

    //connect to the file storate account
    CloudStorageAccount storageAccount = CloudStorageAccount.Parse(" ");

    // Create a CloudFileClient object for credentialed access to File storage.
    CloudFileClient fileClient = storageAccount.CreateCloudFileClient();

    // Get a reference to the file share
    CloudFileShare share = fileClient.GetShareReference("brandofirstsharetest");


    string policyName = "sampleSharePolicy" + DateTime.UtcNow.Ticks;
    CloudFileDirectory rootDir = null;
    CloudFileDirectory fileDir = null;

    // Ensure that the share exists.
    if (share.Exists())
    {

        // Get existing permissions for the share.
        FileSharePermissions permissions = await share.GetPermissionsAsync();
        //if the SharedAccessPolicies is exists just get the SharedAccessPolicies
        if (permissions.SharedAccessPolicies.Count > 0)
        {
                policyName = permissions.SharedAccessPolicies.First().Key;
                SharedAccessFilePolicy sharedPolicy = permissions.SharedAccessPolicies.First().Value;
                sharedPolicy.SharedAccessExpiryTime = DateTime.UtcNow.AddHours(8);
                await share.SetPermissionsAsync(permissions);                  
        }
        else
        {
            // Create a new shared access policy and define its constraints.
            SharedAccessFilePolicy sharedPolicy = new SharedAccessFilePolicy()
            {
                SharedAccessStartTime = DateTime.UtcNow.AddMinutes(-15),
                SharedAccessExpiryTime = DateTime.UtcNow.AddHours(8),
                Permissions = SharedAccessFilePermissions.Read | SharedAccessFilePermissions.Write
            };
            permissions.SharedAccessPolicies.Add(policyName, sharedPolicy);
            await share.SetPermissionsAsync(permissions);
        }


        // Add the shared access policy to the share's policies. Note that each policy must have a unique name.


        // Generate a SAS for a file in the share and associate this access policy with it.
        rootDir = share.GetRootDirectoryReference();
    }

    CloudFile file = rootDir.GetFileReference("Penjs.png");
       string sasToken = file.GetSharedAccessSignature(null, policyName);
       string tick = $"&{ DateTimeOffset.UtcNow.Ticks}";
       Uri fileSasUri = new Uri(file.StorageUri.PrimaryUri.ToString() + sasToken + tick);
于 2017-06-14T04:57:52.360 回答