C#抽象类多泛型类型问题：派生类构造函数传参类型不匹配

你的代码核心问题是泛型类型不匹配：

• 派生类ProviderClassyChangesProposedThingieSection继承的是ThingieSection<ProviderClassyChangesProposedSummaryThingie>，所以基类构造函数要求的参数是List<Thingie<ProviderClassyChangesProposedSummaryThingie>>，但你传入的是List<Thingie<Classy>>，这两个列表类型不兼容（默认Thingie<T>不支持协变）。
• 你之前尝试拆分双泛型但没解决，是因为没给泛型加正确约束，也没理清泛型参数的对应关系。

这里提供两种可行的修正方式：

方式一：让Thingie支持协变（推荐） #

把Thingie<T>改成协变接口（C#中类不能做协变，接口可以），这样Thingie<Classy>可以隐式转换为其派生类对应的泛型接口，同时调整ThingieSection的泛型参数为实体类型：

using System.Collections.Generic;

// 改成协变接口，out关键字实现协变
public interface IThingie<out T>
{
    string TextStuff { get; }
    string Generate();
}

public abstract class Thingie<T> : IThingie<T>
{
    public string TextStuff { get; private set; }
    protected Thingie(T workFlowEntity, string category)
    {
        // 初始化逻辑
    }
    public abstract string Generate();
}

// ThingieSection泛型参数绑定实体类型T
public abstract class ThingieSection<T>
{
    public string Title { get; private set; }
    public string TextStuff { get; private set; }
    public List<IThingie<T>> Thingies { get; private set; }

    protected ThingieSection(string title, string textStuff, List<IThingie<T>> thingies)
    {
        Title = title;
        TextStuff = textStuff;
        Thingies = thingies;
    }
    public abstract string Generate();
}

// 派生类指定实体类型为Classy
public class ProviderClassyChangesProposedThingieSection : ThingieSection<Classy>
{
    public ProviderClassyChangesProposedThingieSection(string title, string content, List<IThingie<Classy>> thingies) 
        : base(title, content, thingies)
    {
    }

    public override string Generate() => throw new System.NotImplementedException();
}

public class ProviderClassyChangesProposedSummaryThingie : Thingie<Classy>
{
    public ProviderClassyChangesProposedSummaryThingie(Classy workFlowEntity, string category) 
        : base(workFlowEntity, category)
    {
    }

    public override string Generate() => throw new System.NotImplementedException();
}

public abstract partial class Classy
{
}

方式二：给ThingieSection添加双泛型参数 #

如果不想改接口，就给ThingieSection两个泛型参数，分别指定实体类型和具体的Thingie派生类，并添加约束：

using System.Collections.Generic;

public abstract class Thingie<T>
{
    public string TextStuff { get; private set; }
    protected Thingie(T workFlowEntity, string category)
    {
    }
    public abstract string Generate();
}

// TEntity是实体类型，TThingie是具体Thingie派生类，约束TThingie必须继承自Thingie<TEntity>
public abstract class ThingieSection<TEntity, TThingie> where TThingie : Thingie<TEntity>
{
    public string Title { get; private set; }
    public string TextStuff { get; private set; }
    public List<TThingie> Thingies { get; private set; }

    // 构造函数接收List<TThingie>，如需更宽松的List<Thingie<TEntity>>也可调整
    protected ThingieSection(string title, string textStuff, List<TThingie> thingies)
    {
        Title = title;
        TextStuff = textStuff;
        Thingies = thingies;
    }

    public abstract string Generate();
}

// 派生类指定实体类型Classy、Thingie派生类为ProviderClassyChangesProposedSummaryThingie
public class ProviderClassyChangesProposedThingieSection : ThingieSection<Classy, ProviderClassyChangesProposedSummaryThingie>
{
    public ProviderClassyChangesProposedThingieSection(string title, string content, List<ProviderClassyChangesProposedSummaryThingie> thingies) 
        : base(title, content, thingies)
    {
    }

    public override string Generate() => throw new System.NotImplementedException();
}

public class ProviderClassyChangesProposedSummaryThingie : Thingie<Classy>
{
    public ProviderClassyChangesProposedSummaryThingie(Classy workFlowEntity, string category) 
        : base(workFlowEntity, category)
    {
    }

    public override string Generate() => throw new System.NotImplementedException();
}

public abstract partial class Classy
{
}

• 方式一的协变接口更灵活，允许传入任何继承自Thingie<Classy>的子类列表；
• 方式二的双泛型参数更明确，强制约束Thingie的具体类型，适合需要严格类型检查的场景。

内容的提问来源于stack exchange，提问作者Eric