Update mongodb

Src/Asp.NetCore2/MongoDbTest/UnitTest/QuerySelect.cs

@@ -2,6 +2,7 @@
 using MongoDB.Driver;
 using MongoDB.Driver.Linq;
 using MongoDbTest.DBHelper;
+using SqlSugar;
 using SqlSugar.MongoDb;
 using System;
 using System.Collections.Generic;
@@ -114,6 +115,12 @@ namespace MongoDbTest
             }).ToList();
             if (list11.First().Age != 12) Cases.ThrowUnitError();
             if (list11.First().Age2 != 13) Cases.ThrowUnitError();
+
+            var list12= db.Queryable<Student>().Select(it => new
+            {
+                Age = -it.Age  
+            }).ToList();
+            if(list12.First().Age!=-11) Cases.ThrowUnitError();
         }
         [SqlSugar.SugarTable("UnitStudent1231sds3z1")]
         public class Student : MongoDbBase

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

@@ -27,7 +27,15 @@ namespace SqlSugar.MongoDb
         public BsonValue Visit(Expression expr)
         {
             expr = MongoDbExpTools.RemoveConvert(expr);
-
+            if (expr.NodeType == ExpressionType.Negate) 
+            {
+                expr=(expr as UnaryExpression).Operand; 
+                var value=new ExpressionVisitor(context,visitorContext).Visit(expr);
+                var isMemember = MongoDbExpTools.GetIsMemember(expr);
+                if (isMemember)
+                    value = $"${value}";
+                return new BsonDocument("$multiply", new BsonArray { -1, value });
+            }
             switch (expr)
             {
                 case BinaryExpression binary:

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

@@ -73,6 +73,11 @@ namespace SqlSugar.MongoDb
             return false;
         }
 
+
+        public static bool GetIsMemember(Expression expr)
+        {
+            return expr is MemberExpression member && member.Expression is ParameterExpression;
+        }
         internal static Expression RemoveConvert(Expression item)
         {
             for (int i = 0; i < 10; i++)

Src/Asp.NetCore2/SqlSugar.MongoDbCore/ExpToSql/VisitorItems/BinaryExpressionTranslator/Helper.cs

@@ -8,6 +8,7 @@ namespace SqlSugar.MongoDb
 {
     public partial class BinaryExpressionTranslator
     {
+
         private static bool IsEq(string op)
         {
             return op == "$eq";