Change the Expression of a (existing) field Parameter Table via script

[NaHolla]

I have a table which is defind as a field Parameter (which I've customized)

TableName = "TOP-Kategorie"

Now, I'd like to update the expression

var targetTable = Model.Tables["TOP-Kategorie"];

var MyNewExpression = ReadFile(@"U:...\TabularMeasures\TOP-Kategorie.csv"); // this works

targetTable.Expression = MyNewExpression ; //not working

how do I change the exression? Thanks!

[otykier]

Are you connected to Power BI Desktop while trying to run this script? If so, could you try to enable the Allow unsupported modeling operations option under Tools > Preferences > Power BI Desktop:

[NaHolla]

Hi,
I´m connected to PowerBI. I'v enebled the setting, but it still comes to an error, (transladed from german) :
TabularEditor.TomWrapper.Table contains no definition for Expression and no MethodExpression could be found

[NaHolla]

error code CS1061

[otykier]

oh I see - you didn't mention that you got an error message in your original post - so I just assumed the script ran without error but didn't change anything.

In any case, it's an easy fix. You just need to explicitly cast the table to type CalculatedTable before attempting to access the Expression property. Like so:

var targetTable = Model.Tables["TOP-Kategorie"];
var MyNewExpression = ReadFile(@"U:...\TabularMeasures\TOP-Kategorie.csv"); // this works

// Explicit cast to CalculatedTable should let you assign the Expression property:
(targetTable as CalculatedTable).Expression = MyNewExpression ;

[NaHolla]

Thanks! now it is working!