fix(CardUpload): 增加去重逻辑

Author: ArgoZhang

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;
     }