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C#基于Mongo的官方驱动手撸一个Super简易版MongoDB-ORM框架

作者：Peter`Pan　　发布时间：2021-06-05 17:27:50　

标签：C#,MongoDB,ORM,框架

如题,在GitHub上找了一圈想找一个MongoDB的的ORM框架,未偿所愿,就去翻了翻官网(https://docs.mongodb.com/drivers/csharp/)

看了看文档发现官方的驱动功能已经相当强大了并且更新速度很快

2.3之后得驱动版本已经支持 .Net 5,而且方法都已支持Task ,可以配合async , await.使用 ,同时也支持Lambda表达式及表达式树官方是这么说的(https://mongodb.github.io/mongo-csharp-driver/2.12/what_is_new/)

官方得驱动如此强大了,还找什么ORM框架,我们自己基于官方驱动手撸一个简易版的,首先简单讲一下设计思路

要求1:首先要有一个对象实体基类,为什么要创建实体对象基类?是因为官方驱动支持的实体类与Collection得映射必须要有id字段,对应数据库中得"_id",并且这个字段是ObjectIDl类型,像这样

public class Person
{
[BsonId]
[BsonElement("_id")]
public ObjectId ID { get; set; }
}

所以创建实体基类是为了免去每个实体类都要创建这个id的冗余代码.

要求2:实现实体类与Collection得自动映射自动创建数据库连接.这一部分实现就稍微复杂一些,首先我们需要自定义一个Attribute,用于获取获取集合名称,然后创建一个管理器实现一些自动映射的初始化操作

要求3:实现Repository仓储类.提供简单得CRUD方法. 这一部分就比较简单了,通过封装直接调用官方的驱动提供的API,实现CURD操作

开始实现之前记得添加一下官方的驱动包直接在Nuget搜索MongoDB.Driver 安装就可以了 ,我这里使用的是2.12.3版本

第一步:创建对象实体基类

[DataContract]
[Serializable]
[BsonIgnoreExtraElements(Inherited = true)] //当BSON文档被反序列化时，每个元素的名称用于在类映射中查找匹配的成员。通常，如果没有找到匹配的成员，将抛出异常。如果要在反序列化期间忽略其他元素使用这个特性
public abstract class MongoEntityBase : IMongoEntityBase<string>
{
protected MongoEntityBase()
{
DB_ID = ObjectId.GenerateNewId().ToString(); //对id进行初始化
}

[DataMember][BsonElement("_id")]
[BsonRepresentation(BsonType.ObjectId)] //因为 ObjectId 这个结构体是不能序列化的,所以使用 [BsonRepresentation(BsonType.ObjectId)] 标记为这个字符串ID在mongo中代表ObjectId
public virtual string DB_ID { get; set; }
}

public interface IMongoEntityBase<TKey>
{
[BsonId]
TKey DB_ID { get; set; }
}
public interface IMongoEntityBase : IMongoEntityBase<string>
{
}

第二步:实现实体类与Collection的自动映射;

我们需要先创建一个Attribute类,用于标记实体类来获取实体类对应的集合名称,如下:

[AttributeUsage(AttributeTargets.Class, Inherited = true)]
public class CollectionNameAttribute : Attribute
{
public CollectionNameAttribute(string name)

{
if (string.IsNullOrEmpty(name)) throw new ArgumentException("Empty collectionname not allowed", "name");

this.Name = name;
}

public string Name { get; private set; } //定义一个属性用于获取Collection名称
}

接下来实现一个管理器,用于自动映射,数据库连接的自动映射,官方驱动其实已经提供了实体类的自动映射,我们只需要接着稍微封装一下,官方自动映射demo如下:

有一部分准备工作要做,那就是需要在配置文件添加一个数据库连接的配置,用于连接数据库;

接下实现我们的管理器,这一部分是核心,实现了类与数据库Collection的自动映射,并自动创建出了mongo连接

internal static class GlobleManage<T>
{
private static string _tableName;
private static string _dateBaseName;
private static string _mongoServerSettings;
private static IMongoCollection<T> _mongoCollection;

public static IMongoCollection<T> MongoCollection
{
get => _mongoCollection;

}
public static string DateBaseName
{
get => _dateBaseName;
}

public static string MongoServerSettings
{
get => _mongoServerSettings;
}
public static string TableName
{
get => _tableName;
}

static GlobleManage()
{
Init();
}

private static void Init()
{
//初始化连接字符串
string[] parm = ConfigurationManager.ConnectionStrings["MongoServerSettings"].ConnectionString.Split('/');

_dateBaseName = parm.Last();
_mongoServerSettings = ConfigurationManager.ConnectionStrings["MongoServerSettings"].ConnectionString.Replace(@"/" + _dateBaseName, ":27017");

//根据实体类标注好的Attribute获取表名
var entitytype = typeof(T);
var attr = Attribute.GetCustomAttribute(entitytype, typeof(CollectionNameAttribute));
//若Attribute不为空获取标注的表名
if (attr != null)
{
_tableName = ((CollectionNameAttribute)attr).Name;

}
else
{
//否则如果类型是MongoEntityBase的派生类获取类名作为表名
if (typeof(MongoEntityBase).IsAssignableFrom(entitytype))
{
// No attribute found, get the basetype
while (!entitytype.BaseType.Equals(typeof(MongoEntityBase)))
{
entitytype = entitytype.BaseType;
}
}
_tableName = entitytype.Name;
}

//添加实体类映射
BsonClassMap.RegisterClassMap<T>(cm => cm.AutoMap());

_mongoCollection = new MongoClient(_mongoServerSettings).GetDatabase(_dateBaseName).GetCollection<T>(_tableName);
}
}

第三步:实现Repository仓储类.提供简单的CRUD方法

首先,先创建仓储类的泛型接口

public interface IRepository<T> where T : IMongoEntityBase<string>
{
IMongoCollection<T> Collection { get; }

bool Add(T entity);
bool Delete(T delete, Expression<Func<T, bool>> conditions = null);
bool Update(T update, Expression<Func<T, bool>> conditions = null);
List<T> Find(Expression<Func<T, bool>> conditions = null);

泛型仓储类实现接口,通过管理器获取自动映射得到的 IMongoCollection

public class Repository<T> : IRepository<T> where T : IMongoEntityBase<string>
{

private IMongoCollection<T> _mongoCollection = GlobleManage<T>.MongoCollection;
public IMongoCollection<T> Collection => _mongoCollection;

public bool Add(T entity)
{
try
{
_mongoCollection.InsertOne(entity);
return true;
}
catch (Exception)
{
throw;
}

}
public bool Delete(T delete, Expression<Func<T, bool>> conditions = null)
{
try
{
string _id = string.Empty;
if (conditions == null)
{
foreach (var item in delete.GetType().GetProperties())
{
if (item.Name == "DB_ID" && item.GetValue(delete) != null)
{
_id = item.GetValue(delete).ToString();
var result = _mongoCollection.DeleteOne(new BsonDocument("_id", BsonValue.Create(new ObjectId(_id))));
return result.IsAcknowledged;
}
}
}
var res = _mongoCollection.DeleteOne(conditions);
return res.IsAcknowledged;
}
catch (Exception)
{
throw;
}
}

public bool Update(T update, Expression<Func<T, bool>> conditions = null)
{
try
{

ObjectId _id;
var options = new ReplaceOptions() { IsUpsert = true };
if (conditions == null)
{
foreach (var item in update.GetType().GetProperties())
{
if (item.Name == "DB_ID" && item.GetValue(update) != null)
{
_id = new ObjectId(item.GetValue(update).ToString());
var result = _mongoCollection.ReplaceOne(new BsonDocument("_id", BsonValue.Create(_id)), update, options);
return result.IsAcknowledged;
}
}
}
var res = _mongoCollection.ReplaceOne(conditions, update, options);
return res.IsAcknowledged;
}
catch (Exception)
{

throw;
}
}

public List<T> Find(Expression<Func<T, bool>> conditions = null)
{
try
{
if (conditions == null)
{
conditions = t => true;
}

return _mongoCollection.Find(conditions).ToList() ?? new List<T>();

}
catch (Exception)
{
throw;
}
}
}

简易版的ORM框架就算是基本完成,接下来使用这个框架完成一些CRUD操作

首先,创建一个实体类,并且继承 MongoEntityBase

[Serializable]
public class Person : MongoEntityBase
{
[BsonConstructor]
public Person(string name, int age, string guid, EnumGender gender)
{

Name = name;
Age = age;
Guid = guid;
Gender = gender;
}
public string Name { get; set; }
public int Age { get; set; }
public string Guid { get; set; }
public EnumGender Gender { get; set; }
public List<Person> Students { get => students; set => students = value; }
public Pet Pet { get => pet; set => pet = value; }

private Pet pet;

public override string ToString()
{
return "DB_ID:" + this.DB_ID + " " + "user:" + Name + " " + "age:" + Age + " " + "guid:" + Guid + " " + "Gender:" + Gender.ToString() + " " + "宠物叫" + Pet.Name + "," + Pet.Age + "岁了";
}
private List<Person> students;

}
public enum EnumGender
{
男,
女
}

public class Pet
{
private string name;
private int age;

public string Name { get => name; set => name = value; }
public int Age { get => age; set => age = value; }
}

然后创建一个窗体测试一下我们的CRUD功能,调用很简单只需要一句 IRepository<Person> _IRepository = new Repository<Person>();

public partial class Form1 : Form
{
private IRepository<Person> _IRepository = new Repository<Person>();
private Random random = new Random();
public Form1()
{
InitializeComponent();
}

//ADD
private void button1_Click(object sender, EventArgs e)
{
Person person = new Person("张三", 8, Guid.NewGuid().ToString(), EnumGender.男);
person.Students = new List<Person>() { new Person("张小三1", 8, Guid.NewGuid().ToString(), EnumGender.男),
new Person("张小三2", 8, Guid.NewGuid().ToString(), EnumGender.男)
,new Person("张小三3", 8, Guid.NewGuid().ToString(), EnumGender.男)
,new Person("张小三4", 8, Guid.NewGuid().ToString(), EnumGender.男)};
person.Pet = new Pet() { Name = "旺财", Age = 3 };
_IRepository.Add(person);
richTextBox1.Text += "添加成功!\r\n";
}
//Find
private void button2_Click(object sender, EventArgs e)
{
var id = textBox1.Text.Trim();
var list = _IRepository.Find(t => t.DB_ID.Equals(id));
richTextBox1.Text += "Find成功:" + "\r\n ";
foreach (var item in list)
{
richTextBox1.Text += item.ToString() + "\r\n ";
}
}

//Delete
private void button3_Click(object sender, EventArgs e)
{
var id = textBox1.Text.Trim();
//var res = _IRepository.Delete(t => t.DB_ID.Equals(id));
var rese = _IRepository.Find(t => t.DB_ID.Equals(id)).FirstOrDefault();
var res = _IRepository.Delete(rese);
richTextBox1.Text += id + "删除:" + res;/*res.IsAcknowledged + res.DeletedCount;*/
}
//Update
private void button4_Click(object sender, EventArgs e)
{
var guid = textBox1.Text.Trim();
Person person = _IRepository.Find(t => t.DB_ID.Equals(guid)).FirstOrDefault();
person.Name = "改过之后的名字" + random.Next(1, 10);
var res = _IRepository.Update(person);
richTextBox1.Text += guid + "更新:" + res;

}
//Clear
private void button5_Click(object sender, EventArgs e)
{
textBox1.Clear();
richTextBox1.Clear();
}

//FindAll
private void button6_Click(object sender, EventArgs e)
{
var list = _IRepository.Find();
richTextBox1.Text += "FindAll成功:" + "\r\n ";
foreach (var item in list)
{
richTextBox1.Text += item.ToString() + "\r\n";
}
}
}

简易版本的功能基本都实现,实际上,一个成熟的ORM框架还有好多工作要做

链接: https://pan.baidu.com/s/1t9xbfQXhb6iz5QJeC0WLOQ

提取码: y9d2

来源：https://www.cnblogs.com/pandefu/p/14769022.html

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C#基于Mongo的官方驱动手撸一个Super简易版MongoDB-ORM框架

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