C# 动态创建类，动态创建表，支持多库的数据库维护方案

public class CodeFirstTable1
{
        [SugarColumn(IsIdentity = true, IsPrimaryKey = true)]
        public int Id { get; set; }
        public string Name { get; set; }
        //ColumnDataType 自定格式的情况 length不要设置 （想要多库兼容看4.2和9）
        [SugarColumn(ColumnDataType = "Nvarchar(255)")]
        public string Text { get; set; }
        [SugarColumn(IsNullable = true)]//可以为NULL
        public DateTime CreateTime { get; set; }
}
  
/***创建单个表***/
db.CodeFirst.SetStringDefaultLength(200).InitTables(typeof(CodeFirstTable1));//这样一个表就能成功创建了
/***手动建多个表***/
db.CodeFirst.SetStringDefaultLength(200)
.InitTables(typeof(CodeFirstTable1),typeof(CodeFirstTable2));

SugarClient db = new SqlSugarClient(new ConnectionConfig()
{
    DbType = DbType.SqlServer,
    ConnectionString = Config.ConnectionString3,
    InitKeyType = InitKeyType.Attribute,
    IsAutoCloseConnection = true,
    ConfigureExternalServices = new ConfigureExternalServices()
    {
        EntityService = (s, p) =>
        {
            //如果是Order实体进行相关配置
            p.IfTable<Order>()
            .UpdateProperty(it => it.id, it =>
            {
                it.IsIdentity = true;
                it.IsPrimarykey = true;
            })
            .UpdateProperty(it => it.Name, it => {
                it.Length = 100;
                it.IsNullable = true;
   
            })
            .OneToOne(it => it.Item, nameof(Order.ItemId));
               
            //如果Custom实体进行相关配置
             p.IfTable<Custom>()
             .UpdateProperty(it => it.id, it =>
             {
                it.IsIdentity = true;
                it.IsPrimarykey = true;
             })
              .UpdateProperty(it => it.Text, it => {
                it.DataType= StaticConfig.CodeFirst_BigString;//支持多库的MaxString用法
              })
               
                           
            //可以结合全局逻辑一起使用，下面的和上面的有冲突的话，下面会覆盖上面的
                
               
            //统一设置 nullable等于isnullable=true
            //低版本C#看标题2.2
             if(p.IsPrimaryKey==false&&new NullabilityInfoContext()
                         .Create(c).WriteState is NullabilityState.Nullable)
             {
                           p.IsNullable = true;
             }
               
                
                
        }
    }
});
//性能说明：
//EntityService 相同实体只会执行一次性不需太操作

var type = db.DynamicBuilder().CreateClass("UnitEntityA",
               new SugarTable()
               {
                   TableDescription = "表备注",
                   //DisabledUpdateAll=true 可以禁止更新只创建
               }
           )
          .CreateProperty("Id", typeof(int), new SugarColumn() { IsPrimaryKey = true, IsIdentity = true, ColumnDescription = "列备注" })
          .CreateProperty("Name", typeof(string), new SugarColumn() {Length=200, ColumnDescription = "列备注" })
          .BuilderType();
 
           db.CodeFirst.InitTables(type);

//例1 获取所有表
var tables = db.DbMaintenance.GetTableInfoList(false);//true 走缓存 false不走缓存
foreach (var table in tables)
{
     Console.WriteLine(table.Description);//输出表信息
       
     //获取列信息
     //var columns=db.DbMaintenance.GetColumnInfosByTableName("表名",false);
}
  
//例2
db.DbMaintenance.IsAnyTable("tablename",false)//验证表名是否缓存不走缓存

[TenantAttribute("1")]//对应ConfigId
public class C1Table
{
   public string Id { get; set; }
}
   
[TenantAttribute("2")]
public class C2Table
{
    public string Id { get; set; }
}

//通过ConfigId进行数据库区分
var db = new SqlSugarClient(new List<ConnectionConfig>()
{
 //这儿声名所有上下文都生效
 new ConnectionConfig(){ConfigId="0",DbType=DbType.SqlServer,ConnectionString=..,IsAutoCloseConnection=true},
 new ConnectionConfig(){ConfigId="1",DbType=DbType.MySql,ConnectionString=..,IsAutoCloseConnection=true  }
});
//自动跨库联表查询
var query5 = db.QueryableWithAttr<Order>()//如果MySql和SqlServer自动支持同服务器的跨库联表查询
         .LeftJoin<Custom>   ((o, cus ) => o.CustomId == cus.Id)//多个条件用&&
         .LeftJoin<OrderDetail> ((o, cus, oritem) => o.Id == oritem.OrderId)
         .Where(o => o.Id == 1) 
         .Select((o, cus , oritem) => new ViewOrder { Id = o.Id, CustomName = cus.Name })
         .ToList(); 
//手动跨库联表查询 ，这种方式结合dblink可以跨服务器
var query5 = db.Queryable().As("xxx.表名")
         .LeftJoin<Custom>   ((o, cus ) => o.CustomId == cus.Id ,"yyyy.表名")
         .LeftJoin<OrderDetail> ((o, cus, oritem) => o.Id == oritem.OrderId ,"zzzz.名表")
         .Where(o => o.Id == 1) 
         .Select((o, cus , oritem) => new ViewOrder { Id = o.Id, CustomName = cus.Name })
         .ToList();

db.QueryFilter
.AddTableFilter<IDeletedFilter>(it => it.IsDeleted==false)//IDeletedFilter是自定义接口,继承这个接口的实体有效
.AddTableFilterIF<ITenantFilter>(isAdmint==false,it=>it.OrgId==用户OrgId);//ITenantFilter自定义接口
  
//用例1：单条语句清空，只影响当前语句
db.Queryable<Order>().ClearFilter().ToList();//所有过滤器都无效
db.Queryable<Order>().ClearFilter<IDeletedFilter>().ToList();//只有IDeletedFilter过滤器无效
db.Queryable<Order>().ClearFilter<IDeletedFilter,ITenantFilter>().ToList();//IDeletedFilter+ITenantFilter无效
    
//用例2：当前上下文清空 ，不会影响其他请求，只是当前请求清空
db.QueryFilter.Clear();
db.QueryFilter.Clear<IDeletedFilter>();
  
//用例3：清空并还原 ，不会影响其他请求，只是当前请求清空
db.QueryFilter.ClearAndBackup();//有多个重载 ClearAndBackup<T,T2>();
db.Queryable<Order>().ToList();
db.QueryFilter.Restore();//还原过滤器 (适合下面代码还需要过滤器情况)

var list=db.Queryable< Order >()
.Select(it => new
        {
          CustomId = it.CustomId,
          OrderId = it.Id,
          OrderName = it.Name,
          CustomList = SqlFunc.Subqueryable< Custom >().Where(c => c.Id == it.CustomId).ToList()
        })
       .ToList();

public class DictionaryConvert : ISugarDataConverter
{
public SugarParameter ParameterConverter<T>(object value, int i)
{
//该功能ORM自带的IsJson就能实现这里只是用这个用例来给大家学习
var name = "@myp" + i;
var str = new SerializeService().SerializeObject(value);
return new SugarParameter(name, str);
}
 
public T QueryConverter<T>(IDataRecord dr, int i)
{
//打断点调试
//该功能ORM自带的IsJson就能实现这里只是用这个用例来给大家学习
var str = dr.GetValue(i) + "";
return new SerializeService().DeserializeObject<T>(str);
}
}
//使用自定义转换器
[SugarColumn(ColumnDataType="varchar(2000)",SqlParameterDbType=typeof(DictionaryConvert))]
public Dictionary<string, object> DcValue { get; set; }//5.1.3.53-preview08