Update mongodb

Src/Asp.NetCore2/MongoDb.Ado.data/MongoDbDataReader.cs

@@ -65,6 +65,7 @@ namespace MongoDb.Ado.data
                 return typeof(string);
             }
             if (obj == null) return typeof(object);
+            if (obj is BsonNull) return typeof(object);
             return BsonTypeMapper.MapToDotNetValue(obj).GetType();
         }
         public override float GetFloat(int ordinal) => (float)GetValue(ordinal);

Src/Asp.NetCore2/MongoDbTest/OrmTest/OrmTest.cs

@@ -37,6 +37,8 @@ namespace MongoDbTest
 
             var list3= db.Queryable<OrderInfo>().Skip(1).Take(1).ToList();
 
+            var list4 = db.Queryable<OrderInfo>().OrderByDescending(it=>it.Price).ToList();
+
             //测试生成SQL性能
             TestSqlBuilder(db);
         }

Src/Asp.NetCore2/SqlSugar.MongoDbCore/ExpToSql/MongoNestedTranslator.cs

@@ -11,7 +11,12 @@ namespace SqlSugar.MongoDbCore
     {
         public static BsonDocument Translate(Expression expr, MongoNestedTranslatorContext context)
         {
-            return (BsonDocument)new ExpressionVisitor(context).Visit(expr);
+            var result = new ExpressionVisitor(context).Visit(expr);
+            if (result is BsonString bs) 
+            {
+                result = new BsonDocument("fieldName", bs);
+            }
+            return (BsonDocument)result;
         }
     }
 }

Src/Asp.NetCore2/SqlSugar.MongoDbCore/MongoDb/SqlBuilder/MongoDbQueryBuilder.cs

@@ -1,4 +1,5 @@
-using System;
+using MongoDB.Bson;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -80,6 +81,27 @@ namespace SqlSugar.MongoDb
             }
             #endregion
 
+            #region OrderBy
+            var order = this.GetOrderByString;
+            var orderByString = this.GetOrderByString?.Trim();
+            if (!string.IsNullOrEmpty(orderByString) && orderByString.StartsWith("ORDER BY ", StringComparison.OrdinalIgnoreCase))
+            {
+                order = order.Substring("ORDER BY ".Length).Trim();
+
+                int lastSpace = order.LastIndexOf(' ');
+                string jsonPart = order.Substring(0, lastSpace).Trim();
+                string directionPart = order.Substring(lastSpace + 1).Trim().ToUpper();
+
+                var bson = MongoDB.Bson.Serialization.BsonSerializer.Deserialize<BsonDocument>(jsonPart);
+                if (bson.Contains("fieldName"))
+                {
+                    var field = bson["fieldName"].AsString;
+                    var direction = directionPart == "ASC" ? 1 : -1;
+                    operations.Add($"{{ \"$sort\": {{ \"{field}\": {direction} }} }}");
+                }
+            }
+            #endregion
+
             sb.Append($"aggregate {this.GetTableNameString} ");
             sb.Append("[");
             sb.Append(string.Join(", ", operations));