如何从阵列中复制 <unsigned short> 在C CLI中使用unsigned short []？

Question

I am working on a C++ CLI wrapper for a C API. The C API has a structure that contains an array of four unsigned shorts and an array of four ints. So I have created a similar class for the C# code to use when calling into the wrapper function.

// C Structure
typedef struct c_Struct_
{
  unsigned short   uShorts[4];
  int     ints[4];
} c_Struct;


// C++ CLI Class
public ref class CliClass
{
public:
  property array<unsigned short>^ UnsignedShorts
  {
    array<unsigned short>^ get()
    {
      return _unsignedShorts;
    }
  }
  property array<int>^ Ints
  {
    array<int>^ get()
    {
      return _ints;
    }
  }

  CliClass(array<unsigned short>^ us, array<int> i)
  {
    _unsignedShorts = us;
    _ints = i;
  }
private:
  array<unsigned short>^ _unsignedShorts;
  array<int>^ _ints;
}

Now we come to my question. I have added an internal method to the the CLI class to create a struct:

internal:
  c_Struct ToStruct()
  {
    c_Struct results;
    results.uShorts[0] = UnsignedShorts[0];
    results.uShorts[1] = UnsignedShorts[1];
    results.uShorts[2] = UnsignedShorts[2];
    results.uShorts[3] = UnsignedShorts[3];
    results.ints[0] = Ints[0];
    results.ints[1] = Ints[1];
    results.ints[2] = Ints[2];
    results.ints[3] = Ints[3];
    return results;
  }

but I get the error: IntelliSense: a value of type "System::Object ^" cannot be assigned to an entity of type "unsigned short" for each assignment. What is the proper syntax for this?

Answer 1

首先取消装箱参考类型，试试这个：

results.uShorts[0] = (unsigned short)UnsignedShorts[0];

Answer 2

The code is correct, you'll see that your program compiles just fine. Nothing is being boxed. This is a bug in the IntelliSense parser. A rather strange one, hard to imagine how it fumbles this. Not entirely uncommon, the parser was made by another company. The Edison Design Group, pretty famous for writing the only compiler that was ever able to implement the C++03 standard correctly. C++/CLI gives them heartburn though.

Two basic workarounds, you could use the field instead of the property:

   c_Struct ToStruct() {
        c_Struct results;
        results.uShorts[0] = _unsignedShorts[0];
        // etc...
   }

But that doesn't fix a problem you'd have with code that uses the class. You could make them indexed properties instead:

property unsigned short UnsignedShorts[int]
{
    unsigned short get(int index) {
        return _unsignedShorts[index];
    }
}
// Same for the Ints property.

Answer 3

Another work-around is to assign to a temporary local variable first.

array<int> ^temp = ArrayOfIntsProperty;
int j = temp[0];

This only affects properties - it appears that functions returning managed arrays work as expected when the call is indexed.