I’m a FoxPro/VB programmer but new to C# and struggling with API calls. Any help would very much be appreciated. Does anyone have an example or experience of making similar API calls.

I’ve initialised the API:

[DllImport("User32.dll")]
static extern bool EnumDisplaySettings(long lpszDeviceName, long iModeNum, DEVMODE lpDevMode);

I’ve defined (and initialised) the required structure:

struct DEVMODE
{
public DEVMODE(string deviceName, string formName)
{
dmDeviceName = deviceName;
dmSpecVersion = 0;
dmDriverVersion = 0;
dmSize = 0;
dmDriverExtra = 0;
dmFields = 0;
dmOrientation = 0;
dmPaperSize = 0;
dmPaperLength = 0;
dmPaperWidth = 0;
dmScale = 0;
dmCopies = 0;
dmDefaultSource = 0;
dmPrintQuality = 0;
dmColor = 0;
dmDuplex = 0;
dmYResolution = 0;
dmTTOption = 0;
dmCollate = 0;
dmFormName = formName;
dmUnusedPadding = 0;
dmBitsPerPel = 0;
dmPelsWidth = 0;
dmPelsHeight = 0;
dmDisplayFlags = 0;
dmDisplayFrequency = 0;
}
string dmDeviceName;
int dmSpecVersion;
int dmDriverVersion;
int dmSize;
int dmDriverExtra;
long dmFields;
int dmOrientation;
int dmPaperSize;
int dmPaperLength;
int dmPaperWidth;
int dmScale;
int dmCopies;
int dmDefaultSource;
int dmPrintQuality;
int dmColor;
int dmDuplex;
int dmYResolution;
int dmTTOption;
int dmCollate;
string dmFormName;
int dmUnusedPadding;
int dmBitsPerPel;
long dmPelsWidth;
long dmPelsHeight;
long dmDisplayFlags;
long dmDisplayFrequency;
}

Finally I’ve made my call:

DEVMODE devMode = new DEVMODE(" "," ")
bool returnValue ;
returnValue = EnumDisplaySettings(0, 0, devMode);

The program builds but errors when attempting to execute the last line above with - “Object reference not set to an instance of an object”

Thanks,
Gary Drudge-Coates.