C#•15mo 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•15mo ago

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

mindhardt•15mo ago

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

Will PittengerOP•15mo ago

OK.

mindhardt•15mo ago

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

Will PittengerOP•15mo ago

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

mindhardt•15mo 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•15mo ago

Message Not Public

Yup•15mo ago

I have the ultimate solution for this

Unknown User•15mo ago

Message Not Public

Yup•15mo ago

PHP

MODiX•15mo ago

That command had an error

UnknownCommand: Unknown command.

Remove your reaction to delete this message

mindhardt•15mo ago

$bam

MODiX•15mo ago

User bammed successfully.

Yup•15mo ago

Unknown command $bam @Hin

MODiX•15mo ago

User bammed successfully.

Will PittengerOP•15mo ago

Bam?

Unknown User•15mo ago

Message Not Public

mindhardt•15mo ago

Yup

Unknown User•15mo ago

Message Not Public

Will PittengerOP•15mo ago

Yes. Thanks. Used to classes.

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✅ Null check not enough to safely convert from nullable enum

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