为什么通用结构不能不受管理？

Question

请看这段代码：

namespace ConsoleApp
{
    public struct MyPoorGenericStructThatCannotBeUnmanaged<T> where T: unmanaged
    {
        public T Field;
    }

    public class MyClass<T> where T: unmanaged
    {
    }

    class Program
    {
        static void Main()
        {
            // The type 'MyPoorGenericStructThatCannotBeUnmanaged<int>' must be a non-nullable value type, 
            // along with all fields at any level of nesting, 
            // in order to use it as parameter 'T' in the generic type or method 'MyClass<T>'
            var obj = new MyClass<MyPoorGenericStructThatCannotBeUnmanaged<int>>(); 
        }
    }
}

编译失败错误：

The type 'MyPoorGenericStructThatCannotBeUnmanaged' must be a non-nullable value type, along with all fields at any level of nesting, in order to use it as parameter 'T' in the generic type or method 'MyClass'

然而MyPoorGenericStructThatCannotBeUnmanaged<int>是一个不可空值类型，它在任何嵌套值处的所有字段确实是不可空值类型。它由泛型类型约束 where T: unmanaged

确保

为什么？

Answer 1

在解决限制之前，您可以使用基于不安全的解决方法。

解决方法可能如下所示：

public unsafe class ArrayOfGenericStructs<TStruct> : IDisposable where TStruct:struct
{
    private void* pointer;

    public ArrayOfGenericStructs(int size)
    {
        pointer = (void*) Marshal.AllocHGlobal(Unsafe.SizeOf<TStruct>() * size);
    }

    public bool IsDisposed { get; private set; }

    public void Dispose()
    {
        if (IsDisposed) return;
        IsDisposed = true;
        if (pointer != null) Marshal.FreeHGlobal(new IntPtr(pointer));
        pointer = null;
    }

    public ref TStruct this[int index]
    {
        get
        {
            return ref Unsafe.AsRef<TStruct>(Unsafe.Add<TStruct>(pointer, index));
        }
    }
}

为什么通用结构不能不受管理？

Why generic structs cannot be unmanaged?

c#

c#-7.3