[Table(Name = "Bas_Client")]
public partial class Client
{
    [Column(IsKey = true)]
    public virtual int ClientId { get; set; }
    public virtual string ClientCode { get; set; }
    public virtual string ClientName { get; set; }
    public virtual int CloudServerId { get; set; }
    [ForeignKey("CloudServerId")]
    public IList<CloudServer> CloudServer { get; set; }
}

[Table(Name = "Sys_CloudServer")]
public partial class CloudServer
{
    [Column(IsKey = true)]
    public virtual int CloudServerId { get; set; }
    public virtual string CloudServerCode { get; set; }
    public virtual string CloudServerName { get; set; }
}

// 声明数据库链接字符串
const string connString = "Server=.;Database=***;uid=**;pwd=**;pooling=true;connect timeout=10;";
// 实例化数据上下文
// SqlServer
var context = new SqlServerDbContext(connString);
var data = context.GetTable<Client>().Where(a => a.ClientId <= 10).ToList();
data = context
    .GetTable<Client>()
    .Include(a => a.CloudServer, a => new
    {
        CloudServerCode = a.CloudServer.CloudServerCode
    })
    .ToList();