feat: ✨ 前端表格高级筛选 (#100)

* chore: 🔨 css 基础单位

[skip ci]

* fix: 🐛 ca2263 System.Enum.GetValues<TEnum>()

[skip ci]

* feat: ✨ 前端表格高级筛选

[skip ci]

src/backend/NetAdmin.Host/Middlewares/SafetyShopHostMiddleware.cs

@@ -0,0 +1,44 @@
+namespace NetAdmin.Host.Middlewares;
+
+/// <summary>
+///     安全停机中间件
+/// </summary>
+/// <remarks>
+///     放在所有中间件最前面
+/// </remarks>
+public sealed class SafetyShopHostMiddleware(RequestDelegate next)
+{
+    private static long _connections;
+    private static bool _hostStopping;
+
+    /// <summary>
+    ///     当前连接数
+    /// </summary>
+    public static long Connections => Interlocked.Read(ref _connections);
+
+    /// <summary>
+    ///     停机处理
+    /// </summary>
+    public static void OnStopping()
+    {
+        Volatile.Write(ref _hostStopping, true);
+        while (Interlocked.Read(ref _connections) > 0) {
+            Thread.Sleep(10);
+        }
+    }
+
+    /// <summary>
+    ///     主函数
+    /// </summary>
+    public async Task InvokeAsync(HttpContext context)
+    {
+        if (Volatile.Read(ref _hostStopping)) {
+            context.Response.StatusCode = (int)HttpStatusCode.ServiceUnavailable;
+            return;
+        }
+
+        _ = Interlocked.Increment(ref _connections);
+        await next(context).ConfigureAwait(false);
+        _ = Interlocked.Decrement(ref _connections);
+    }
+}