int.TryParse in U-SQL

Question

I am trying to validate if a string variable in a U-SQL SELECT can be interpreted as an integer, som I am trying to use int.TryParse to replace "0" and "" with default value of two and everything above 10 with 10. Here is the code:

DECLARE @maxAvgkWh double = 100.00;
DECLARE @defaultM2 int = 90;
DECLARE @defaultPersons int = 2;


// Extracting installations and their information
@forDecisionTree =
    EXTRACT [InstallationId] string,
            [PrimaryHeatingType] string,
            [Persons] string,
            [SquareMeters] string,
            [LatestAvgDailykWh] double
    FROM "adl://some text file in azure data lake"
    USING Extractors.Tsv(skipFirstNRows : 1, silent : true);


// Making sure that NULLS and zeroes and abnormal values are replaced with default values
@forDecisionTreeHouseTypeReplNulls =
    SELECT  [InstallationId],
            [PrimaryHeatingType],
            (
                ! int.TryParse(Persons, out var _pers) || _pers <= 0 ?  
                    @defaultPersons :
                    _pers > 10 ?
                        10 :
                        _pers
            ).ToString() AS [Persons],
            (
                ! int.TryParse([SquareMeters], out var _m2) || _m2 <= 0 ?  
                    @defaultM2 :
                    _m2 > 500 ?
                        500 :
                        _m2
            ).ToString() AS [SquareMeters],
            [LatestAvgDailykWh]
    FROM @forDecisionTreeHouseType
    WHERE [LatestAvgDailykWh] < @maxAvgkWh;

I keep getting the following error:

C# error CS1003: Syntax error, ',' expected

at token '_pers', line 108 near the ###:

---

...! int.TryParse([Persons], out var ### _pers) || _pers <= 0 ? ...

Answer 1

TryParse is not one of the functions you can call directly. It has to be wrapped as an inline function. A simple example:

@output =
    SELECT FirstName,
               (
                (Func<string, int?>)
                (inputString =>  // input_paramater
                    { 
                        int outputValue;
                        return int.TryParse(inputString, out outputValue) ? (int?)outputValue : (int?)null;
                    }
                 )
            ) (Salary) AS someDate

    FROM @Employees;

Examples here and here.