read record

[John Lai]

Hi, I have a DB storing student's ID and name. Both are variable-length 
string. Records are written to memory like this:
12\x00Amy Chan\x00
3456789\x00Ben Yau\x00

Provided the student ID, I want to get his name. The following function gets 
fatal error at MemHandleLock(). Please help.

Err GetStudentName(DmOpenRef dbP, Char *stdID, Char *stdName)
{
        Err err = errNone;
        Int16 numRecords;
        Int16 index;
        Boolean found = false;
        char *text;
	numRecords = DmNumRecords(dbP);

        if (numRecords > 0)
        {
                for (index=0; index<numRecords && !found; index++)
                {
                        MemHandle recordH = DmQueryRecord(dbP, index);
                        if (recordH)
                        {
                                text = (char *) MemHandleLock(recordH); // fatal alert 
here, free handle
                                if (text!= NULL && StrCompare(text, stdID) == 0)
                                {
                                        text += StrLen(text) + 1; // get student name
                                        found = true;
                                        StrCopy(stdName, text);
                                }
                                MemHandleUnlock(recordH);
                        }
                }
        }
        return err;
}
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