C#•13mo ago

✅ Null check not enough to safely convert from nullable enum

I have a class declaring an enum and a nullable value for that enum:

public readonly StdModeTypes? smt;

public readonly StdModeTypes? smt;

I then try to reference that field from a second class:

if(cmodeCur.smt != null)
    mapModesWithStdTypes[cmodeCur.smt] = cmodeCur;

if(cmodeCur.smt != null)
    mapModesWithStdTypes[cmodeCur.smt] = cmodeCur;

Yet even with the null check, the IDE is insisting that smt could be null and won't let me use the value:

Error    CS1503    Argument 1: cannot convert from 'BestChat.IRC.Data.Defs.ChanMode.StdModeTypes?' to 'BestChat.IRC.Data.Defs.ChanMode.StdModeTypes'

Error    CS1503    Argument 1: cannot convert from 'BestChat.IRC.Data.Defs.ChanMode.StdModeTypes?' to 'BestChat.IRC.Data.Defs.ChanMode.StdModeTypes'

What's going on?

20 Replies

Will PittengerOP•13mo ago

Given the smt field is readonly, isn't that enough to ensure the value hasn't changed?

mindhardt•13mo ago

With value types the nullability is different With ref types it is just an annotation, more or less

Will PittengerOP•13mo ago

OK.

mindhardt•13mo ago

But with value types it is an actual type, in your case Nullable<StdModeTypes>

Will PittengerOP•13mo ago

Too bad the compiler doesn't automatically unwrap it for you when the value can't be null.

mindhardt•13mo ago

if(cmodeCur.smt.HasValue)
    mapModesWithStdTypes[cmodeCur.smt.Value] = cmodeCur;

if(cmodeCur.smt.HasValue)
    mapModesWithStdTypes[cmodeCur.smt.Value] = cmodeCur;

.HasValue is the same as != null or is not null In this case

if(cmodeCur.smt is { } smt)
    mapModesWithStdType[smt] = cmodeCur;

if(cmodeCur.smt is { } smt)
    mapModesWithStdType[smt] = cmodeCur;

This is also an option if you like patterns

Unknown User•13mo ago

Message Not Public

Yup•13mo ago

I have the ultimate solution for this

Unknown User•13mo ago

Message Not Public

Yup•13mo ago

PHP

MODiX•13mo ago

That command had an error

UnknownCommand: Unknown command.

Remove your reaction to delete this message

mindhardt•13mo ago

$bam

MODiX•13mo ago

User bammed successfully.

Yup•13mo ago

Unknown command $bam @Hin

MODiX•13mo ago

User bammed successfully.

Will PittengerOP•13mo ago

Bam?

Unknown User•13mo ago

Message Not Public

mindhardt•13mo ago

Yup

Unknown User•13mo ago

Message Not Public

Will PittengerOP•13mo ago

Yes. Thanks. Used to classes.

Gaming

Programming

✅ Null check not enough to safely convert from nullable enum