Update mongodb

Src/Asp.NetCore2/SqlSugar.MongoDbCore/Tools/UtilMethods.cs

@@ -1,4 +1,5 @@
-using System;
+using MongoDB.Bson;
+using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Data;
@@ -471,6 +472,13 @@ namespace SqlSugar.MongoDb
             }
             return dic;
         }
+
+        internal static BsonValue GetBsonValue(bool isMember, BsonValue field)
+        {
+            if (isMember) return "$" + field;
+            else
+                return field;
+        }
         //public static object ConvertDataByTypeName(string ctypename,string value)
         //{
         //    var item = new ConditionalModel() {