Echelon LNS - Manual (Page 247)

LNS Programmer's Guide 233
names defined for the SNVT_defr_term type, such as DFT_TERM_LAST, to the
FormattedValue property of the DataPoint. You should also note that this is the only
property that enforces range limits (i.e. the Value and RawValue properties do not
enforce these restrictions). You can use the Value property of the DataPoint to obtain
the numeric value associated with the enumerator, as shown in the following code
sample:
Dim MyFormatSpec as LcaFormatSpec
Dim MyDataPoint as LcaDataPoint
Set MyFormatSpec = MyDataPoint.FormatSpec
MyFormatSpec.FormatType = lcaFormatTypeNamed
MyFormatSpec.FormatName = “SNVT_defr_term”
Set MyDataPoint.FormatSpec = MyFormatSpec
MyDataPoint.FormattedValue = DFT_TERM_LAST
After executing the code shown above, the Value property would return 3 - the numeric
value that corresponds to the DFT_TERM_LAST enumeration. Remember that LNS will
not perform range checking on the Value property, and no exception will be thrown if
you try to write an illegal value to the property.
If you write an illegal value to the Value property at this point (i.e. a value that does not
correspond to one of the valid enumeration names for the type) and then read the
FormattedValue property, no exception will be thrown. However, the value will not be
converted to an enumeration name since there is no enumeration associated with the
value. However, if you attempt to write the illegal value to the FormattedValue
property at this point, an exception will be thrown.
You could expand the previous example to retrieve all the valid enumeration names that
can be assigned to a data point by adding the sample code shown below. You will need to
use the MinValue and MaxValue properties to perform this task. These properties
contain the maximum numeric value (i.e. the value stored in the Value property) that
can be applied to the data point. This code checks every value between the data point’s
minimum and maximum values. If the data stored in the Value property does not match
the data stored in the FormattedValue property, it indicates that the FormattedValue
property represents one of the valid enumeration names:
Dim i as Long
For i = MyDataPoint.MinValue To MyDataPoint.MaxValue
MyDataPoint.Value = i
IF MyDataPoint.FormattedValue <> MyDataPoint.Value THEN
cboEnumList.AddItem(MyDataPoint.FormattedValue)
END IF
Next
Using Configuration Properties In a Monitor and Control
Application
This section provides guidelines and instructions to follow when creating an LNS
application to monitor and control configuration property values. Configuration property
access is generally less efficient than network variable access, so for performance
reasons, you should only use LNS to monitor and control the values of configuration