Converting a string with arguments to Double

[brianA32ZM]

Hello, 

I am attempting to pull the expression from a parameter, "ActuatorPosition_TopBladeToActuator_Standard", then replace 2 variables, "Blade_Qty" and "Blade_Size"), with new values.  Then covert to double so that I can evaluated the formula. I am struggling finding a solution to covert from string to double; any help to point me in the correct direction would be appreciated. Thank you

'Parameter("Frame-GS", "ActuatorPosition_TopBladeToActuator_Standard") = Max(0 in,Floor(( Parameter("Frame-GS", "Blade_Qty") - 0 in ) / 4 ul) * ( ( Parameter("Frame-GS", "Blade_Size") * 2 ul ) ))
T = Parameter.Param("Frame-GS", "ActuatorPosition_TopBladeToActuator_Standard").expression 
logger.info(T)
T = T.replace("Blade_Qty", 5) 
T = T.replace("Blade_Size", 8)
logger.info(T)

[kacper.suchomski]

Maybe this:

Dim str As String = "123.45"
Dim number As Double = CDbl(str)
MessageBox.Show("Value: " & number)

[brianA32ZM]

@kacper.suchomski  thank you. This works if the sting is just a number. The string that I am looking to covert contains a formula: "Max(0 in,Floor(( Parameter("Frame-GS", "Blade_Qty") - 0 in ) / 4 ul) * ( ( Parameter("Frame-GS", "Blade_Size") * 2 ul ) ))"

[WCrihfield · Accepted solution]

Hi @brianA32ZM.  That's a tough one.  If you were dealing directly with a real Inventor API Parameter type object, and accessing its Parameter.Expression property, you always get a String, and the contents of that String will be exactly what you see in the Parameters dialog, in the Equation column, for that parameter.  So, even if it is just a simple numerical value, with no equation, there will still be a numerical value, then a single space, then the abbreviated 'units' specifier text.  In those cases, we can use the Conversion.Val(System.String) method to get just the leading numerical value, without the text that follows it.  However, if it contains an equation, and that equation contains the names of other parameters, and you are wanting to replace the parameter names in it with numerical values, then end up with a Double type value, that's definitely a more complex situation.  You would need a system that would be able to recognize the parameter names within the equation, and then get the numerical values of those parameters, and substitute those into the equation.  At that point you are still working with an equation within a String though, and would then need to 'evaluate' that equation, to get a true numerical value from it.  There are several tools for that type of task.

From the Inventor API Parameters object, we can use the following two methods:

 Parameters.IsExpressionValid followed by Parameters.GetValueFromExpression, which would result in 'database units' value, instead of document or parameter units value, if they are different units.

We also have the same tools available from the Inventor API UnitsOfMeasure object.

UnitsOfMeasure.IsExpressionValid 

UnitsOfMeasure.GetValueFromExpression 

Edit:  Actually, I just remembered that I recently created an iLogic rule for someone else on the forum recently, which goes through all parameters, looks within their Expression, and replaces any parameter names with the values of those parameters.  I will post just the custom Function I created for that case below, in case it gives you some ideas for this case.  It works with the entire Parameters collection though, because in order to recognize the parameter names, it starts by getting the names of all the parameters to a single collection.  Then as it reviews individual Expression Strings, it checks if it 'Contains' any of those parameter names, and if so, gets the value of that parameter, and replaces its name with its numerical value.  You would need to modify it to only effect one parameter at a time, instead of all parameters though.

Function ReplaceParamNamesInParamExpressions(oParams As Inventor.Parameters) As Boolean
	'Design Intent:  should return True only when changes have been made, and False otherwise
	If oParams Is Nothing OrElse oParams.Count = 0 Then Return False
	Dim bChanged As Boolean = False
	Dim oAllParamNames As IEnumerable(Of String) = oParams.Cast(Of Inventor.Parameter).Select(Function(p) p.Name)
	For Each oParam As Inventor.Parameter In oParams
		Dim sExp As String = oParam.Expression
		For Each sParamName As String In oAllParamNames
			If Not sExp.Contains(sParamName) Then Continue For
			Try
				oParam.Expression.Replace(sParamName, oParams.Item(sParamName).Expression)
				bChanged = True
			Catch ex As Exception
				Logger.Error(ex.Message)
			End Try
		Next 'sParamName
	Next 'oParam
	Return bChanged
End Function

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[brianA32ZM]

@WCrihfield Sorry for the delay in my response. You confirmed the complexity of the task I was trying to perform. With that in mind the effort is probably not worth the goal I was attempting to achieve. Thank you for the detail information!

[arichard7PK5R]

Before it was CDbl() but now it's CDblAny(). So for this to work it needs to be that way:

Dim str As String = "123.45"

Dim number As Double = CDblAny(str)

MessageBox.show("Value: " & number)