对泛型类C#中的类型参数调用函数

本文关键字:类型参数 调用 函数 泛型类 | 更新日期: 2023-09-27 18:29:45

如何调用在泛型基类中抽象定义的函数。

我有一个通用

class Class1<T> where T : class, new()

以及从中派生的多个类别,如

Class2: Class1<Class2> 
Class3: Class1<Class3>

通用类有3个功能

1->接受一个动态对象,并将所有值放入派生对象中的相应属性

2->接受ID,在数据库中查找相应的行,将动态对象传递给func1并返回结果

3->返回表中所有行的listall函数

这是的通用代码

public abstract partial class Class1<T> where T : class, new()
{
    public static EntityLayout EntityLayout { get; protected set; }
    [TypeAttributes(TypeAttributes.Options.IsPrimary, TypeAttributes.Options.IsAutoIncrement)]
    /// <summary> Automatically Incremented 64 bit Integer Primary Key
    /// represents the Unique ID of each row in Table </summary>
    public long ID { get; set; }
    /// <summary> Converts the row returned from Database to Object </summary>
    /// <param name="row"></param>
    /// <returns></returns>
    public abstract T GetDetails(dynamic row);
    public static T GetDetails(long ID)
    {
        var row = Shared.SessionWrapper.Current.globaldbcon.QuerySingle("SELECT * FROM [" 
            + EntityLayout.ContainerName + "].["
            + EntityLayout.TableName + "] WHERE ID=@0", ID);
        if (row != null) return GetDetails(row);
        return new T();
    }
    public static List<T> ListAll()
    {
        List<T> result = new List<T>();
        foreach (var row in Shared.SessionWrapper.Current.globaldbcon.Query("SELECT * FROM [" 
            + EntityLayout.ContainerName + "].["
            + EntityLayout.TableName + "]")) result.Add(GetDetails(row));
        return result;
    }
}

示例类实现

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Arinsys.Database;
namespace WebApplication1.Models
{
    [EntityAttributes(EntityAttributes.Options.TestingEnabled)]
    public class Class3 : Class1<Class3>
    {
        static Class3()
        {
            EntityLayout.DisplayName = "Users";
        }
        /// <summary> User ID of the User </summary>
        public long UID { get; set; }
        /// <summary> User ID of the User if defined in Universal Data Store  </summary>
        public long UDSID { get; set; }
        /// <summary> Login ID of User </summary>
        public string LoginID { get; set; }
        /// <summary> Registered email of the user. If not set will be set same as LoginID </summary>
        public string Registeredemail { get; set; }
        [TypeAttributes(TypeAttributes.Options.IsPassword)]
        /// <summary> Password of user </summary>
        public string Password { get; set; }
        /// <summary> A Unique Security Stamp used for activation/deactivation of account or similar intense tasks </summary>
        public string SecurityStamp { get; set; }
        /// <summary> Timezone ID of the Default Timezone of User </summary>
        public string DefaultTimezone { get; set; }
        /// <summary> Current Status of User </summary>
        public string CurrentStatus { get; set; }
        /// <summary> Discriminator which defines the type of user in multi-user heirarchy scenario </summary>
        public string UserType { get; set; }
        /// <summary> Number of failed login attempts in total or same session depending upon configuration. Resets after Successful Login </summary>
        public short FailedAttempts { get; set; }
        /// <summary> Date Time of Last Failed Login Attempt in UTC </summary>
        public DateTime LastFailedAttempt { get; set; }
        /// <summary> Date Time of Last Successful Login in UTC </summary>
        public DateTime LastLogin { get; set; }
        /// <summary> Creation Date of User Account in UTC </summary>
        public DateTime CreationDate { get; set; }
        public override Class3 GetDetails(dynamic row)
        {
            Class3 result = new Class3();
            if (row != null)
            {
                result.ID = Convert.ToInt64(row.ID);
                result.UID = Convert.ToInt64(row.UID);
                result.UDSID = Convert.ToInt64(row.UDSID);
                result.UserType = row.UserType;
                result.LoginID = row.LoginID;
                result.Password = row.Password;
                result.Registeredemail = row.Registeredemail;
                result.SecurityStamp = row.SecurityStamp;
                result.DefaultTimezone = row.DefaultTimezone;
                result.CurrentStatus = row.CurrentStatus;
                result.FailedAttempts = Convert.ToInt16(row.FailedAttempts);
                result.LastFailedAttempt = Convert.ToDateTime(row.LastFailedAttempt);
                result.LastLogin = Convert.ToDateTime(row.LastLogin);
                result.CreationDate = Convert.ToDateTime(row.CreationDate);
            }
            return result;
        }
    }
}

在发布之前,已经花了两周时间到处寻找答案,但找不到解决方案。

我只想让ListAll函数调用1st函数。由于它是抽象定义的,我确信派生类必须有一个实现(即使它可能只是抛出NotImplementException,但实现是有保证的)

我首先通过反射在泛型类中定义了1st函数的实现。虽然这很有效,但它非常慢,通过在控制器动作的开始/结束时启动/停止秒表来进行性能基准测试,仅100排就花了大约35秒,所以它肯定不适合生产使用。

注意事项

  • 静态不能定义为抽象
  • 无法从静态上下文访问实例成员
  • 由于性能问题,无法使用反射

我想可能的解决方案是最接近的(但我无法理解如何在我的情况下使用它们)

  • 将所有方法转换为实例方法并使用singleton
  • 使用接口
  • 在派生类中定义一个静态方法,并假设它将存在于所有类中,如果我这样做,那么在这种情况下如何访问T上的静态方法

我想要实现的是ListAll函数应该调用接受动态对象的1st函数。

有些问题非常接近这些,但没有一个能解决我的疑问。

堆栈溢出Q1堆栈溢出Q2堆栈溢出Q3

对泛型类C#中的类型参数调用函数

看起来设计应该像这个

public abstract partial class Class1<T> where T : Class1<T>, new()
{
    protected abstract void Load(dynamic row);
    private static T GetItem(dynamic row)
    {
        var item = new T();
        if (row != null)
            item.Load(row);
        return item;        
    }
    public static T GetDetails(long ID)
    {
        var row = Shared.SessionWrapper.Current.globaldbcon.QuerySingle("SELECT * FROM [" 
            + EntityLayout.ContainerName + "].["
            + EntityLayout.TableName + "] WHERE ID=@0", ID);
        return GetItem(row);
    }
    public static List<T> ListAll()
    {
        List<T> result = new List<T>();
        foreach (var row in Shared.SessionWrapper.Current.globaldbcon.Query("SELECT * FROM [" 
            + EntityLayout.ContainerName + "].["
            + EntityLayout.TableName + "]")) result.Add(GetItem(row));
        return result;
    }
}

以及示例实现

public class Class3 : Class1<Class3>    {
{
    // ...
    protected override void Load(dynamic row)
    {
        // No need to check for null, it is enforced by the base class
        ID = Convert.ToInt64(row.ID);
        UID = Convert.ToInt64(row.UID);
        // ...
    }
}

基本上,您探索了.NET泛型类约束(T : Class1<T>)支持的奇怪的重复模板模式,以确保派生类包含抽象的Load方法,而new T()部分由new()约束强制执行。