Revert "refactor: 精简代码"

This reverts commit 114d3ad.

Author: ArgoZhang

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

@@ -266,14 +266,17 @@ private SelectedItem? SelectedRow
             ?? Rows.Where(i => !i.IsDisabled).FirstOrDefault()
             ?? GetVirtualizeItem(CurrentValueAsString);
 
-        if (_init && DisableItemChangedWhenFirstRender)
+        if (item != null)
         {
+            if (_init && DisableItemChangedWhenFirstRender)
+            {
 
-        }
-        else
-        {
-            _ = SelectedItemChanged(item);
-            _init = false;
+            }
+            else
+            {
+                _ = SelectedItemChanged(item);
+                _init = false;
+            }
         }
         return item;
     }
@@ -377,12 +380,12 @@ private bool TryParseSelectItem(string value, [MaybeNullWhen(false)] out TValue
             ?? GetVirtualizeItem(value);
 
         // support SelectedItem? type
-        result = (TValue)(object)SelectedItem;
+        result = SelectedItem != null ? (TValue)(object)SelectedItem : default;
         validationErrorMessage = "";
         return SelectedItem != null;
     }
 
-    private SelectedItem GetVirtualizeItem(string value)
+    private SelectedItem? GetVirtualizeItem(string value)
     {
         SelectedItem? item = null;
         if (_result.Items != null)