!1334 fix(#I3LVBZ): MultiSelect OnParameterSet should check CurrentValueAsString

* docs: 更改级联参数示例
* fix: 修复级联更改数据源不正确问题

src/BootstrapBlazor.Shared/Pages/Samples/MultiSelects.razor.cs

@@ -30,11 +30,11 @@ namespace BootstrapBlazor.Shared.Pages
         /// <param name="item"></param>
         private async Task OnCascadeBindSelectClick(SelectedItem item)
         {
+            // 模拟异步获取数据源
             await Task.Delay(100);
-            Items2.Clear();
             if (item.Value == "Beijing")
             {
-                Items2.AddRange(new SelectedItem[]
+                Items2 = new List<SelectedItem>(new[]
                 {
                     new SelectedItem("1","朝阳区") { Active = true },
                     new SelectedItem("2","海淀区")
@@ -42,12 +42,16 @@ namespace BootstrapBlazor.Shared.Pages
             }
             else if (item.Value == "Shanghai")
             {
-                Items2.AddRange(new SelectedItem[]
+                Items2 = new List<SelectedItem>(new[]
                 {
                     new SelectedItem("1","静安区"),
                     new SelectedItem("2","黄浦区") {Active = true },
                 });
             }
+            else
+            {
+                Items2 = new List<SelectedItem>();
+            }
             StateHasChanged();
         }
 

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

@@ -105,7 +105,6 @@ namespace BootstrapBlazor.Components
         /// 获得/设置 绑定数据集回调方法
         /// </summary>
         [Parameter]
-        [NotNull]
         public EventCallback<IEnumerable<SelectedItem>> ItemsChanged { get; set; }
 
         /// <summary>
@@ -211,7 +210,7 @@ namespace BootstrapBlazor.Components
             await base.OnParametersSetAsync();
 
             // 通过 Value 对集合进行赋值
-            if (Value != null)
+            if (!string.IsNullOrEmpty(CurrentValueAsString))
             {
                 var list = CurrentValueAsString.Split(',', StringSplitOptions.RemoveEmptyEntries);
                 foreach (var item in Items)
@@ -480,7 +479,7 @@ namespace BootstrapBlazor.Components
         /// 更改组件数据源方法
         /// </summary>
         /// <param name="items"></param>
-        [Obsolete("请使用双向绑定 @bind-Items 来获取 Items 集合变化，更改数据源只需更改 Items 参数即可")]
+        [Obsolete("更改数据源 Items 参数即可")]
         public void SetItems(List<SelectedItem>? items)
         {
             Items = items;