Lỗi vô cùng khó hiểu: Cannot use an expression of type 'byte*' as an argument to a dynamically dispatched operation

Mình có đoạn code này:

unsafe public Task<object> uncompress16(dynamic input)
{
  var inputHexAddress = Convert.ToUInt64((string)input.inputHexAddress, 16);
  if (inputHexAddress == 0) throw new ArgumentException("Hex address is in invalid form!");
  var outputGetter = (Func<object, Task<object>>)input.outputGetter;
  var inputArr = (byte*)(new UIntPtr(inputHexAddress).ToPointer());
  var inputLen = (int)input.inputLen;
  var compressedData = new UnsafeArray(inputArr, inputLen);
  int size = (int)compressedData[1] + ((int)compressedData[2] << 8) + ((int)compressedData[3] << 16);
  return outputGetter(size).ContinueWith<object>(uncompress16_stage2);
}
unsafe private object uncompress16_stage2(Task<object> lastTask)
{
  var output = (dynamic)lastTask.Result;
  var outputHexAddress = Convert.ToUInt64((string)output.outputHexAddress, 16);
  if (outputHexAddress == 0) throw new ArgumentException("Hex address is in invalid form!");
  var outputArr = (byte*)(new UIntPtr(outputHexAddress).ToPointer());
  var outputLen = output.outputLen;
  var uncompressedData = new UnsafeArray(outputArr, outputLen);
  return output;
}

Kết quả là dòng này:

var uncompressedData = new UnsafeArray(outputArr, outputLen);

Báo lỗi:

Cannot use an expression of type 'byte*' as an argument to a dynamically dispatched operation.

Nhưng dòng này:

var compressedData = new UnsafeArray(inputArr, inputLen);

Lại không sao cả:

Đây là class UnsafeArray:

public class UnsafeArray
{
  unsafe private byte* _array;
  unsafe private int _len;
  unsafe public UnsafeArray(byte* array, int len)
  {
    if (array == null) throw new NullReferenceException("Array is null!");
    if (len < 0) throw new ArgumentOutOfRangeException("Array length cannot be negative!");
    this._array = array;
    this._len = len;
  }
  unsafe public byte this[int key]
  {
    get
    {
      if (key < 0 && key >= _len) throw new ArgumentOutOfRangeException("Index of array is out of bound.");
      return _array[key];
    }
    set
    {
      if (key < 0 && key >= _len) throw new ArgumentOutOfRangeException("Index of array is out of bound.");
      _array[key] = value;
    }
  }
}