C＃调用C＋＋DLL时，出现尝试读取或写入受保护的内存。这通常指示其他内存已损坏。
[DllImport("Iocp_dll.dll", EntryPoint = "_SendPacket@16", CharSet = CharSet.Auto)]
public static extern int SendPacket(ulong time, int index,ref byte[] buf, int length);

private unsafe void btnStart_Click(object sender, EventArgs e)
{
byte[] sun = new byte[9];
string dig = "dig";
byte[] encodedBytes = Encoding.ASCII.GetBytes(dig);


sun[0] = (byte)(len / 256);
sun[1] = (byte)(len % 256);
sun[2] = message[0];
sun[3] = message[1];
for (i = 0; i < encodedBytes.Length; i++)
{
sun[4 + i] = encodedBytes[i];
}
byte[] crc_data = new byte[5];
crc_data[0] = message[0];
crc_data[1] = message[1];

for (int j = 0; j < 3; j++)
{
crc_data[j + 2] = encodedBytes[j];
}
ushort crcm = (ushort)CRC.MakeCRC(crc_data, 5);

sun[7] = (byte)(crcm % 256);
sun[8] = (byte)(crcm / 256);
Iocp.SendPacket(tt, index,ref sun, 9);

}

[解决办法]
ulong 改 uint :
[DllImport("Iocp_dll.dll", EntryPoint = "_SendPacket@16", CharSet = CharSet.Auto)]
public static extern int SendPacket(uint time, int index,ref byte[] buf, int length);

[解决办法]
WinAPI的long类型是32位的,而C#的long是64位的,会引发PInvokeStackImbalance错误。因此需要将原来的long类型改为int类型,C#中int是32位的