- 增加 EfCoreFluentApi 扩展包，接近 efcore fluentApi 的使用习惯；#4

- 增加 ColumnAttribute 属性 InsertValueSql，插入数据的时候指定用 sql 值；

Extensions/FreeSql.Extensions.EfCoreFluentApi/EfCoreColumnFluent.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using System.Linq.Expressions;
+using FreeSql.DataAnnotations;
+
+namespace FreeSql.Extensions.EfCoreFluentApi
+{
+    public class EfCoreColumnFluent
+    {
+        ColumnFluent _cf;
+
+        internal EfCoreColumnFluent(ColumnFluent tf)
+        {
+            _cf = tf;
+        }
+
+        public ColumnFluent Help() => _cf;
+
+        public EfCoreColumnFluent HasColumnName(string name)
+        {
+            _cf.Name(name);
+            return this;
+        }
+        public EfCoreColumnFluent HashColumnType(string dbtype)
+        {
+            _cf.DbType(dbtype);
+            return this;
+        }
+        public EfCoreColumnFluent IsRequired()
+        {
+            _cf.IsNullable(false);
+            return this;
+        }
+        public EfCoreColumnFluent HasMaxLength(int length)
+        {
+            _cf.StringLength(length);
+            return this;
+        }
+        public EfCoreColumnFluent HasDefaultValueSql(string sqlValue)
+        {
+            _cf.InsertValueSql(sqlValue);
+            return this;
+        }
+        public EfCoreColumnFluent IsRowVersion()
+        {
+            _cf.IsVersion(true);
+            return this;
+        }
+        //public EfCoreColumnFluent HasConversion(Func<object, string> stringify, Func<string, object> parse)
+        //{
+        //    return this;
+        //}
+    }
+}