Update mongodb

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

@@ -3,6 +3,7 @@ using System.Data.Common;
 using System.Data;
 using MongoDB.Bson;
 using MongoDB.Driver;
+using System.Linq;
 
 namespace MongoDb.Ado.data
 {
@@ -73,11 +74,24 @@ namespace MongoDb.Ado.data
             if (operation == "find")
             {
                 var filter = string.IsNullOrWhiteSpace(json) ? FilterDefinition<BsonDocument>.Empty : BsonDocument.Parse(json);
-                var document = collection.Find(filter).FirstOrDefault();
+
-                return document;
+                // 设置投影排除 "_id" 字段，确保返回的结果不包含 _id 字段
+                var projection = Builders<BsonDocument>.Projection.Exclude("_id");
+
+                // 执行查询并限制返回一条记录
+                var document = collection.Find(filter).Project(projection).FirstOrDefault();
+
+                // 如果查询到结果且文档非空，则获取第一个字段的值
+                if (document != null && document.Elements.Any())
+                {
+                    var firstElement = document.Elements.First();  // 获取第一个字段（列）
+                    return firstElement.Value;  // 返回该字段的值
+                }
+
+                return null; // 如果没有结果或没有字段，返回 null
             }
 
-            throw new NotSupportedException("只支持 find 操作。");
+           return null;
         }
 
         protected override DbDataReader ExecuteDbDataReader(CommandBehavior behavior)

Src/Asp.NetCore2/MongoDbTest/AdoTest.cs

@@ -21,18 +21,29 @@ namespace MongoDbTest
 
         private static void MongoDbCommandTest()
         {
-            var connection = new MongoDbConnection(DbHelper.SqlSugarConnectionString);
+            //ExecuteReader
-            connection.Open();
+            { 
-            MongoDbCommand mongoDbCommand = new MongoDbCommand(" find b { age: { $gt: 31 } }", connection);
+                var connection = new MongoDbConnection(DbHelper.SqlSugarConnectionString);
-            using (var reader = mongoDbCommand.ExecuteReader()) 
+                connection.Open();
-            {
+                MongoDbCommand mongoDbCommand = new MongoDbCommand(" find b { age: { $gt: 31 } }", connection);
-                while (reader.Read()) 
+                using (var reader = mongoDbCommand.ExecuteReader())
                 {
-                    var name=reader.GetString("name");
+                    while (reader.Read())
-                    var age = reader.GetInt32("age");
+                    {
+                        var name = reader.GetString("name");
+                        var age = reader.GetInt32("age");
+                    }
                 }
+                connection.Close();
+            }
+            //ExecuteScalar
+            {
+                var connection = new MongoDbConnection(DbHelper.SqlSugarConnectionString);
+                connection.Open();
+                MongoDbCommand mongoDbCommand = new MongoDbCommand(" find b { age: { $gt: 31 } }", connection);
+                var value=mongoDbCommand.ExecuteScalar();
+                connection.Close();
             }
-             connection.Close();
         }
 
         private static void MongoDbConnectionTest()