C# yana bambanta nau'ikan da zai iya zama daga waɗanda ba zai iya. () suna ba ƙimar nau'i damar riƙe null, (fasali na compiler) suna taimaka wajen kama kutu na null, da (, , ) suna sa aiki tare da yuwuwar-null ƙimar a tsaf da aminci — tackle matsalar jiyya-bayyanin da ke yaduwa.
nullint??.??!int x = 5; // a value type — CANNOT be null
int? y = null; // int? = Nullable<int> — CAN be null
if (y.HasValue) { int val = y.Value; } // check + access
int z = y ?? 0; // default if null
Ba za a iya zama null ta zahiri ta nau'ikan ƙimar ba, amma int? (Nullable<int>) yana bayyanin haka — gida ga bayyanin aminci/bawa bakin aiki (misali database fulani da nullable).
#nullable enable // (on by default in modern projects)
string name = null; // ⚠️ warning — string is non-nullable by default now
string? maybe = null; // ✅ string? explicitly allows null
void Use(string? s) {
Console.WriteLine(s.Length); // ⚠️ warning — s might be null (must check first)
}
Tare da nau'ikan nullable na bayyanin a konewa, compiler yana kula da waɗanne bayyanin za su iya zama null (string?) da waɗanda ba (string) da gargaɗi lokacin da za ka iya ba bayyanin null — kama NullReferenceException bugi lokacin ƙuduri. Wannan babbar sahin C# na zamani ne.
// ?. null-conditional — short-circuits to null instead of throwing
int? len = user?.Name?.Length; // null if user or Name is null (no exception)
user?.DoSomething(); // only calls if user isn't null
// ?? null-coalescing — provide a default
string name = input ?? "Anonymous";
name ??= "fallback"; // assign if currently null
// ! null-forgiving — assert non-null (suppress the warning; use carefully)
string definitelyNotNull = maybe!; // "I know it's not null" — no runtime check
The null-conditional operator (?.) yana karbar saniya sa tsaf daidai da yuwuwar-null ƙimar (da dawo null a maye gurbin taba), da ?? suna ba tsoho — tare suna sa jiyya hada da tsaf da aminci.
Jiyya hada shine ɗaya daga cikin muhimman gida na rubuta aminci C#, tunda NullReferenceException ("kuskuren kuɗi miliyan) shi ne ɗaya daga cikin sauƙun kuskuren lokaci-guida — da C# nau'ikan nullable da ma'aikatan suna magance shi ta jiya, suna sa su da mahimmanci. Nau'ikan nullable na ƙimar (int?) su ne dole don wakilta aminci/bawa bakin aiki (nullable filin database, ƙimar aminci).
Fasalin nullable reference types (yanzu a baje-baje ta tsoho a sabohin .NET aiki) shi ne babbar kariya na haɓakar: ta harin compiler kula da jiyya gargaɗi ɓokakken null dereferences, kama dubu fasali na null bug lokacin ƙuduri maimakon lokaci-guida zuwa — aminci da amma ƙarya.
Ma'aikatan jiyya-hada su ne aiki ta kwanaki-kwanaki da suke sa aiki tare da yuwuwar-null ƙimar da tsaf da aminci: null-conditional operator (?.) yana karbar waje yuwuwar-null jerin (da dawo null maimakon taba), ??/??= suna ba tsoho taushi, da ! suna yanke jiya (don saido dandali).
'Fahimta nau'ikan nullable na ƙimar, sahin kariya na nullable-reference-types, da ma'aikatan jiyya-hada (?., ??, !) ya rintsaye ga rubuta null-aminci, aminci C# da shi hara NullReferenceException — gida da kusan-kusan muhimmanci.
Tun kutu-jiyya bugi su ne gida da C# suna ba kuzari (musamman lokaci-kuduri jiyya takura) don hana su, guida nau'ikan nullable da ma'aikatan jiyya iko mahimmanci, dole-doler fahimta ga rubuta aminci sabohin C#.