Expert Advisor Programming by Andrew R. Young

EXPERT ADVISOR PROGRAMMING
Fig. 3.2 – Alert message
Here are the log contents. The first line is the output from the Alert() function. The second line is
the output of the Print() function. Notice the error, "invalid trade volume", and the fact that the lot
size reported in the log is 0. In this case, the problem is that the lot size is invalid.
16:47:54 Profit Buster EURUSD,H1: Alert: Open Buy Stop Order - Error 131:
invalid trade volume
16:47:54 Profit Buster EURUSD,H1: Bid: 1.5046, Ask: 1.5048, Lots: 0
You can create similar error handling routines for other functions as well, especially for the
OrderModify() and OrderClose() functions. You can also create more sophisticated error handling
routines that provide custom error messages based on the error code, or perform other actions.
For example, if you receive error 130: "invalid stops", you could display a message such as "The stop
loss or take profit price is invalid." Here's an example of how you can do this:
ErrorCode = GetLastError();
string ErrDesc;
if(ErrorCode == 129) ErrDesc = "Order opening price is invalid!";
if(ErrorCode == 130) ErrDesc = "Stop loss or take profit is invalid!";
if(ErrorCode == 131) ErrDesc = "Lot size is invalid!";
string ErrAlert = StringConcatenate("Open Buy Order - Error ",ErrorCode,": ",ErrDesc);
Alert(ErrAlert);
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