Convert VB CLR function to C#

Question

How can I convert below VB.net SQL CLR function to C# CLR Function for a VS SSDT SQL Project?

I need to convert it to C# as it seems that built-in SSDT Project support for CLR functions is C# only? If I could find a way to use the original VB in a way that's compatible with VS SSDT projects and won't break Publish workflow, then I would accept that answer! I found it really easy to compile the .dll into SQL server using T-SQL commands in SSMS... but as soon as I brought it into our SSDT project to incorporate into our next .dacpac release, nothing worked!

SqlFunction(IsDeterministic:=True, IsPrecise:=True)> _
Public Shared Function RegExOptionEnumeration(ByVal IgnoreCase As SqlBoolean, _
             ByVal MultiLine As SqlBoolean, _
                           ByVal ExplicitCapture As SqlBoolean, _
                           ByVal Compiled As SqlBoolean, _
                           ByVal SingleLine As SqlBoolean, _
                           ByVal IgnorePatternWhitespace As SqlBoolean, _
                           ByVal RightToLeft As SqlBoolean, _
                           ByVal ECMAScript As SqlBoolean, _
                           ByVal CultureInvariant As SqlBoolean) _
              As SqlInt32
  Dim Result As Integer
  Result = (IIf(IgnoreCase.Value, RegexOptions.IgnoreCase, RegexOptions.None) Or _
   IIf(MultiLine.Value, RegexOptions.Multiline, RegexOptions.None) Or _
   IIf(ExplicitCapture.Value, RegexOptions.ExplicitCapture, _
                RegexOptions.None) Or _
   IIf(Compiled.Value, RegexOptions.Compiled, RegexOptions.None) Or _
   IIf(SingleLine.Value, RegexOptions.Singleline, RegexOptions.None) Or _
   IIf(IgnorePatternWhitespace.Value, RegexOptions.IgnorePatternWhitespace, _
                RegexOptions.None) Or _
   IIf(RightToLeft.Value, RegexOptions.RightToLeft, RegexOptions.None) Or _
   IIf(ECMAScript.Value, RegexOptions.ECMAScript, RegexOptions.None) Or _
   IIf(CultureInvariant.Value, RegexOptions.CultureInvariant, RegexOptions.None))
  Return (Result)

I have attempted to run the Class through Telerik C# Converter.

Telerik produces below C#:

public class RegularExpressionFunctions
    {
        // 
        // RegExOptions function
        // this is used simply to create the bitmap that is passed to the various 
        // CLR routines

        [SqlFunction(IsDeterministic = true, IsPrecise = true)]
        public static SqlInt32 RegExOptionEnumeration(SqlBoolean IgnoreCase, SqlBoolean MultiLine, SqlBoolean ExplicitCapture, SqlBoolean Compiled, SqlBoolean SingleLine, SqlBoolean IgnorePatternWhitespace, SqlBoolean RightToLeft, SqlBoolean ECMAScript, SqlBoolean CultureInvariant)
        {
            int Result;
            Result = (Interaction.IIf(IgnoreCase.Value, RegexOptions.IgnoreCase, RegexOptions.None) | Interaction.IIf(MultiLine.Value, RegexOptions.Multiline, RegexOptions.None) | Interaction.IIf(ExplicitCapture.Value, RegexOptions.ExplicitCapture, RegexOptions.None) | Interaction.IIf(Compiled.Value, RegexOptions.Compiled, RegexOptions.None) | Interaction.IIf(SingleLine.Value, RegexOptions.Singleline, RegexOptions.None) | Interaction.IIf(IgnorePatternWhitespace.Value, RegexOptions.IgnorePatternWhitespace, RegexOptions.None) | Interaction.IIf(RightToLeft.Value, RegexOptions.RightToLeft, RegexOptions.None) | Interaction.IIf(ECMAScript.Value, RegexOptions.ECMAScript, RegexOptions.None) | Interaction.IIf(CultureInvariant.Value, RegexOptions.CultureInvariant, RegexOptions.None));
            return (Result);
        }
}

All other functions in the Class seem to convert OK with the Telerik converter. I tried searching around for this and it seems that IIf is similar to ternary operators. On this basis, I have tried the following 2 examples, but nothing works...

Attempt 1

[SqlFunction(IsDeterministic = true, IsPrecise = true)]
    public static SqlInt32 RegExOptionEnumeration(SqlBoolean IgnoreCase, SqlBoolean MultiLine, SqlBoolean ExplicitCapture, SqlBoolean Compiled, SqlBoolean SingleLine, SqlBoolean IgnorePatternWhitespace, SqlBoolean RightToLeft, SqlBoolean ECMAScript, SqlBoolean CultureInvariant)
    {
        int Result;
        Result = 
            (IgnoreCase.Value == true ? RegexOptions.IgnoreCase : RegexOptions.None) ||
            (MultiLine.Value ? RegexOptions.Multiline : RegexOptions.None) ||
            (ExplicitCapture.Value ? RegexOptions.ExplicitCapture : RegexOptions.None) || 
            (Compiled.Value ? RegexOptions.Compiled : RegexOptions.None) || 
            (SingleLine.Value ? RegexOptions.Singleline : RegexOptions.None) || 
            (IgnorePatternWhitespace.Value ? RegexOptions.IgnorePatternWhitespace : RegexOptions.None) || 
            (RightToLeft.Value ? RegexOptions.RightToLeft : RegexOptions.None) || 
            (ECMAScript.Value ? RegexOptions.ECMAScript : RegexOptions.None) || 
            (CultureInvariant.Value ? RegexOptions.CultureInvariant : RegexOptions.None);
        return (Result);
    }

Attempt 2

public static object Iif(bool cond, object left, object right)
    {
        return cond ? left : right;
    }

    [SqlFunction(IsDeterministic = true, IsPrecise = true)]
    public static SqlInt32 RegExOptionEnumeration(SqlBoolean IgnoreCase, SqlBoolean MultiLine, SqlBoolean ExplicitCapture, SqlBoolean Compiled, SqlBoolean SingleLine, SqlBoolean IgnorePatternWhitespace, SqlBoolean RightToLeft, SqlBoolean ECMAScript, SqlBoolean CultureInvariant)
    {
        int Result;
        Result = Iif(IgnoreCase.Value, RegexOptions.IgnoreCase, RegexOptions.None) || Iif(MultiLine.Value, RegexOptions.Multiline, RegexOptions.None) || Iif(ExplicitCapture.Value, RegexOptions.ExplicitCapture, RegexOptions.None) || Iif(Compiled.Value, RegexOptions.Compiled, RegexOptions.None) || Iif(SingleLine.Value, RegexOptions.Singleline, RegexOptions.None) || Iif(IgnorePatternWhitespace.Value, RegexOptions.IgnorePatternWhitespace, RegexOptions.None) || Iif(RightToLeft.Value, RegexOptions.RightToLeft, RegexOptions.None) || Iif(ECMAScript.Value, RegexOptions.ECMAScript, RegexOptions.None) || Iif(CultureInvariant.Value, RegexOptions.CultureInvariant, RegexOptions.None);
        return (Result);
    }

Answer 1

The function is building an int with the bitfields of the regex options (which are designed in such a way they can be combined together). So I'd write a utility function and do it something like :-

    static int BitIf(SqlBoolean condition, RegexOptions flag) => condition.Value ? (int) flag : 0;

    static SqlInt32 RegExOptionEnumeration(SqlBoolean IgnoreCase, SqlBoolean MultiLine, SqlBoolean ExplicitCapture, SqlBoolean Compiled, SqlBoolean SingleLine, SqlBoolean IgnorePatternWhitespace, SqlBoolean RightToLeft, SqlBoolean ECMAScript, SqlBoolean CultureInvariant)
    {
            return BitIf(IgnoreCase, RegexOptions.IgnoreCase)
            | BitIf(MultiLine, RegexOptions.Multiline)
            | BitIf(ExplicitCapture, RegexOptions.ExplicitCapture)
            | BitIf(Compiled, RegexOptions.Compiled)
            | BitIf(SingleLine, RegexOptions.Singleline)
            | BitIf(IgnorePatternWhitespace, RegexOptions.IgnorePatternWhitespace)
            | BitIf(RightToLeft, RegexOptions.RightToLeft)
            | BitIf(ECMAScript, RegexOptions.ECMAScript)
            | BitIf(CultureInvariant, RegexOptions.CultureInvariant);
    }
}