为什么更正“可选参数”会导致访问冲突？

与C＃中的Delphi DLL通讯。该函数的Delphi定义是

function oziCreateWP(var Name: pchar; Symbol: integer; lat, lon: double; Altitude: double; 
  wpDate: double; MapDisplayFormat: integer; PointerDirection: integer;
  GarminDisplayFormat: integer; ForeColor, BackColor: integer;
  ProximityDistance: integer; var Description: pchar; FontSize: integer;
  FontStyle: integer; SymbolSize: integer): integer; stdcall;

该函数使用指定参数在指定位置创建一个航路点。返回值是所创建的Waypoint的内部OziExplorer编号。如果以后在程序中操纵Waypoint，则可能需要在本地存储该编号。对于大多数参数，可以将值指定为-1，这意味着使用OziExplorer默认值。**表示以上选项适用于该字段。

Name - the name of the waypoint Symbol - the symbol number; ** lat,lon - the position in decimal degrees (WGS 84 datum) Altitude - in meters (-777 = altitude unknown) wpDate - the format of the date is at the end of this document; -1 = use todays date and time. MapDisplayFormat - 0 to 8; ** PointerDirection - 0 to 3; ** GarminDisplayFormat - 0 to 2; ** ForeColor - RGB color; ** BackColor - RGB color; ** ProximityDistance - in meters (0 = no proximity) Description - text string FontSize - in points; ** FontStyle - 0 = normal; 1 = bold; ** SymbolSize - 17 = normal; **

我的C＃定义是..

[DllImport("oziapi.dll", CharSet = CharSet.Ansi, SetLastError = true, ExactSpelling = true)]
public static extern int oziCreateWP(ref string Name, int Symbol, double lat, double lon,
    double Altitude = oziAltitudeNull, double wpDate = oziDefault,
    int MapDisplayFormat = oziDefault, int PointerDirection = oziDefault,
    int GarminDisplayFormat = oziDefault, int ForeColor = oziDefault,
    int BackColor = oziDefault, int ProximityDistance = oziDefault, 
    ref string Description, int FontSize = oziDefault, 
    int FontStyle = oziDefault, int SymbolSize = oziDefault);

我的实现代码是..

private void btnCreateAManualWP_Click(object sender, EventArgs e)
{
    int nTemp;
    int nAlt = -777;
    int nNegOne = -1;
    int nZero = 0;
    string cName = cWPName.Text;
    string cDescription = "No Description";
    nTemp = oziCreateWP(ref cName, nNegOne, Convert.ToDouble(cWPLat.Text), 
        Convert.ToDouble(cWPLon.Text), nAlt, nNegOne, nNegOne, nNegOne, nNegOne, nNegOne,
        nNegOne, nZero, ref cDescription, nNegOne, nNegOne, nNegOne);
    nTemp = oziRefreshMap();
}

有了这个，我得到了一个CS1737Optional parameters must appear after all required parameters错误消息标记说明。如果我更正定义中的参数顺序和解决此问题的调用，则在运行时会收到“内存访问冲突”错误。