refactor: 移动 _virtualizeElement 到基类

Author: ArgoZhang

src/BootstrapBlazor/Components/Select/MultiSelect.razor

@@ -1,7 +1,7 @@
 @namespace BootstrapBlazor.Components
 @using Microsoft.AspNetCore.Components.Web.Virtualization
 @typeparam TValue
-@inherits SelectBase<TValue>
+@inherits SimpleSelectBase<TValue>
 @attribute [BootstrapModuleAutoLoader("Select/MultiSelect.razor.js", JSObjectReference = true)]
 
 @if (IsShowLabel)

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

@@ -210,9 +210,6 @@ private List<SelectedItem> Rows
 
     private string? ScrollIntoViewBehaviorString => ScrollIntoViewBehavior == ScrollIntoViewBehavior.Smooth ? null : ScrollIntoViewBehavior.ToDescriptionString();
 
-    [NotNull]
-    private Virtualize<SelectedItem>? _virtualizeElement = default;
-
     /// <summary>
     /// OnParametersSet 方法
     /// </summary>

src/BootstrapBlazor/Components/Select/Select.razor

@@ -1,7 +1,7 @@
 @namespace BootstrapBlazor.Components
 @using Microsoft.AspNetCore.Components.Web.Virtualization
 @typeparam TValue
-@inherits SelectBase<TValue>
+@inherits SimpleSelectBase<TValue>
 @attribute [BootstrapModuleAutoLoader(JSObjectReference = true)]
 
 @if (IsShowLabel)

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

@@ -176,9 +176,6 @@ 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;

src/BootstrapBlazor/Components/Select/SimpleSelectBase.cs

@@ -0,0 +1,21 @@
+// 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([email protected]) Website: https://www.blazor.zone
+
+using Microsoft.AspNetCore.Components.Web.Virtualization;
+
+namespace BootstrapBlazor.Components;
+
+/// <summary>
+/// SimpleSelectBase component base class
+/// </summary>
+/// <typeparam name="TValue"></typeparam>
+public class SimpleSelectBase<TValue> : SelectBase<TValue>
+{
+    /// <summary>
+    /// Gets virtualize component instrance
+    /// </summary>
+    [NotNull]
+    protected Virtualize<SelectedItem>? _virtualizeElement = default;
+}