Expression.Evaluate() - how to use it with propertyobject?

[MatLaroche]

Hi,

I code in a process model callback and would like to evaluate an expression with the Runstate.Caller context.

I found the method 

Expression.Evaluate ( evaluationContext, evaluationOptions = EvalOption_NoOptions)

This is exactly what I need. However, if I have a CallingStep.Expr, which is a expression, I can't access the Evaluate() function. It is not available, only the PropertyObjects functions are.

How can I cast it to be an Expression so I can access the function Evaluate?!

I though I could do:

Runstate.CallingStep.Expr.Evaluate(Runstate.Caller, 0x0)

This would return the expression evaluated in the caller context as a PropertyObject.

But it's not the case, I'm missing something so TS know Runstate.CallingStep.Expr is an Expression... even if I add it to Watch panel, it shows it's an expression...

Thank you.

[j_dodek · Accepted solution]

Hi,

Try to use RunState.Caller.AsPropertyObject.EvaluateEx(xxx)

Hope this helps

Juergen

[MatLaroche]

Thanks, I didn't though of do it this way.

This is one way to achieve it, by doing something like:

Runstate.Caller.AsPropertyObject.EvaluateEx(RunState.CallingStep.TS.CustomResults[1].Name, 0x0).GetValString("", 0x0)

This retrieves the string representing the additionnal result[1] name of my step, which is an expression using local variable in the sequence.

Thanks j_dodek.

If anyone would like to also add a comment about using Expression.Evaluate() properly or an example, it would be appreciated.

[j_dodek]

Hi Mat,

Just for more understanding

you wrote:  I'm missing something so TS know Runstate.CallingStep.Expr is an Expression

Is this your "Expression" a Statement step Type ?  

Or is your "Expression" in every Step in Pre/Post/Status or other in stuff

Could  you provide a screen shot that descripes what you are looking for.

I do not understand it.

Regards

Juergen

[MatLaroche]

I have an object of type Expression (from what I understand and from what the watch panel is showing) and I was expecting to be able to use the Evaluate() function.

Expression.Evaluate(seqContext, options)

But it seems that it's a propertyobject because only the function of this type are available.

I've attached a screenshot. Thank you.

[AllenP]

The Expression type in the API is not the same as the Expression type of a PropertyObject.  The Expression PropertyObject type really is just a "labeled" string that lets you know it's supposed to be an expression.

To create an API Expression Object, you need to call Engine.NewExpression.