转移.net core 3.1，为.NET 5做准备

OpenAuth.Repository/Core/BaseEntity.cs

@@ -0,0 +1,24 @@
+namespace OpenAuth.Repository.Core
+{
+    public abstract class BaseEntity
+    {
+        /// <summary>
+        /// 判断主键是否为空，常用做判定操作是【添加】还是【编辑】
+        /// </summary>
+        /// <returns></returns>
+        public abstract bool KeyIsNull();
+
+        /// <summary>
+        /// 创建默认的主键值
+        /// </summary>
+        public abstract void GenerateDefaultKeyVal();
+
+        public BaseEntity()
+        {
+            if (KeyIsNull())
+            {
+                GenerateDefaultKeyVal();
+            }
+        }
+    }
+}