fix(CardUpload): add duplicate filter logic (#7430)

* fix(CardUpload): 增加去重逻辑

* refactor: 代码格式化

Author: ArgoZhang

src/BootstrapBlazor/Components/Upload/DropUpload.razor

@@ -1,4 +1,4 @@
-@namespace BootstrapBlazor.Components
+@namespace BootstrapBlazor.Components
 @inherits FileListUploadBase<string>
 
 @if (IsShowLabel)
@@ -51,7 +51,8 @@
     @if (ShowUploadFileList)
     {
         <UploadPreviewList Items="Files" IsDisabled="@IsDisabled" ShowProgress="@ShowProgress"
-                           OnGetFileFormat="@OnGetFileFormat" OnCancel="OnCancel" CancelIcon="@CancelIcon" LoadingIcon="@LoadingIcon"
+                           OnGetFileFormat="@OnGetFileFormat" OnCancel="OnCancel"
+                           CancelIcon="@CancelIcon" LoadingIcon="@LoadingIcon"
                            InvalidStatusIcon="@InvalidStatusIcon" ValidStatusIcon="@ValidStatusIcon"
                            ShowDownloadButton="@ShowDownloadButton" DownloadIcon="@DownloadIcon" OnDownload="@OnDownload"
                            DeleteIcon="@DeleteIcon" OnDelete="@OnFileDelete">

src/BootstrapBlazor/Components/Upload/UploadBase.cs

@@ -1,4 +1,4 @@
-// Licensed to the .NET Foundation under one or more agreements.
+// Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the Apache 2.0 License
 // See the LICENSE file in the project root for more information.
 // Maintainer: Argo Zhang(argo@live.ca) Website: https://www.blazor.zone
@@ -283,7 +283,13 @@ protected List<UploadFile> GetUploadFiles()
             {
                 _filesCache.AddRange(DefaultFileList);
             }
-            _filesCache.AddRange(UploadFiles);
+            UploadFiles.ForEach(f =>
+            {
+                if (!_filesCache.Contains(f))
+                {
+                    _filesCache.Add(f);
+                }
+            });
         }
         return _filesCache;
     }