refactor: 重构组件变量改用私有字段

Author: ArgoZhang

src/BootstrapBlazor/Components/Select/Select.razor

@@ -48,7 +48,7 @@
                     }
                     else
                     {
-                        <Virtualize ItemSize="RowHeight" OverscanCount="OverscanCount" ItemsProvider="LoadItems" Placeholder="RenderPlaceHolderRow" ItemContent="RenderRow" @ref="VirtualizeElement" />
+                        <Virtualize ItemSize="RowHeight" OverscanCount="OverscanCount" ItemsProvider="LoadItems" Placeholder="RenderPlaceHolderRow" ItemContent="RenderRow" @ref="_virtualizeElement" />
                     }
                 </div>
             }

src/BootstrapBlazor/Components/Select/Select.razor.cs

@@ -144,9 +144,6 @@ public partial class Select<TValue> : ISelect, ILookup
     [Parameter]
     public bool DisableItemChangedWhenFirstRender { get; set; }
 
-    [NotNull]
-    private Virtualize<SelectedItem>? VirtualizeElement { get; set; }
-
     /// <summary>
     /// Gets or sets the bound data set.
     /// </summary>
@@ -247,6 +244,9 @@ public partial class Select<TValue> : ISelect, ILookup
     /// </summary>
     protected override string? RetrieveId() => InputId;
 
+    [NotNull]
+    private Virtualize<SelectedItem>? _virtualizeElement = default;
+
     private string? InputId => $"{Id}_input";
 
     private string _lastSelectedValueString = string.Empty;
@@ -409,7 +409,7 @@ private async Task RefreshVirtualizeElement()
         if (IsVirtualize && OnQueryAsync != null)
         {
             // 通过 ItemProvider 提供数据
-            await VirtualizeElement.RefreshDataAsync();
+            await _virtualizeElement.RefreshDataAsync();
         }
     }
 
@@ -556,7 +556,7 @@ private async Task OnClearValue()
 
         if (OnQueryAsync != null)
         {
-            await VirtualizeElement.RefreshDataAsync();
+            await _virtualizeElement.RefreshDataAsync();
         }
 
         _lastSelectedValueString = string.Empty;