Advertisements I declared a Razor page with an optional parameter: [Parameter] public KeyValuePair<string, T>? Value { get; set; } Which I use in the Razor page markup: @if (Value != null && item.Key == Value.Key) { <span> ….. </span> } Visual Studio complains with the nullable type declared with "?" (if I remove the "?",… Read More Compilation error with nullable parameter in Razor markup
Advertisements I’ve written a simple extension method to help parse a string to a nullable enum type. public static TEnum? ParseNullableEnum<TEnum>(this string? str) where TEnum : Enum { if (str is null) { return null; } if (!Enum.TryParse(typeof(TEnum), str, ignoreCase: true, out var source)) { throw new ArgumentOutOfRangeException(nameof(str), str, null); } return (TEnum)source; } As… Read More Returning null for a nullable enum not allowed
Advertisements I am not understand why this code not working class nullableGenericA<T: Any?>{ fun someMethod(v: T){} fun someMethod(){ someMethod(null) } } error: "Null can not be a value of a non-null type T". How it works? If nullable is not part of type why works this class NullableGenericB<T>(val list: ArrayList<T>){ fun add(obj: T){ list.add(obj) }… Read More Kotlin nullable generic
Advertisements I’m trying to set a array with a null in to a boolean, but I dont know how to do it, here is my code export interface PeriodicElement { caja: boolean; tractor: boolean; } const ELEMENT_DATA: PeriodicElement[] = [ {caja:null, tractor:false} ] >Solution : You can use union types to achieve this. Union Types… Read More Nullable boolean in Angular
Advertisements Flutter shows error Non-nullable instance field ‘_areas’ must be initialized. Maybe this is because of not defining null in lists areas what when defining null Like List? _areas; it shows an error on the index Error: Field ‘_areas’ should be initialized because its type ‘List’ doesn’t allow null. Error Line: List _areas; Here is… Read More Field '_areas' should be initialized because its type 'List<Area>' doesn't allow null
Advertisements I am trying to use SQL queries, but I meet a problem with nullable objects : Here is my code where I define all MySql parameters : MySqlParameter[] listParams = new MySqlParameter[] { new MySqlParameter("id", this.ID), new MySqlParameter("idStock", this.idStock), new MySqlParameter("certificate", this.certificate), new MySqlParameter("idLO", this.launchingOrder.ID), new MySqlParameter("idToleOri", this.toleOri.ID), new MySqlParameter("idTolesOri", string.Join("+", this.idTolesOri)), new MySqlParameter("listInstructions",… Read More set MySqlParameter = -1 if null
Advertisements I’ve created an Azure function in which I’d like to retrieve information from an input blob and set metadata on a newly created output blob. I don’t think I’m setting the metadata correctly however, as I am unable to retrieve it in another part of my application. Azure function code: public static async Task… Read More Azure function – Setting CloudBlockBlob metadata on a new blob
Advertisements In NET 6, I have a repository asynchronously returns string, which may be sourced from REST API or text file. Since the result could be null, the return type is nullable string in a task Task<string?>: public interface IFooRepository { Task<string?> FetchAsync(string path); } One of a concrete class of the repository would look… Read More NET 6 – Nullability of reference types warning
Advertisements I’m creating a clone for a website where parents can create a list of things they need for their newborn baby so other people can buy it for them as a gift. At this moment I’ve managed to insert data into my table and to link that row of data to the user id… Read More LARAVEL: Display lists that belongs to a specific user_id
Advertisements I am completely new to Android Studio and just learned Object-oriented programming. My project requires me to build something on open-source code. I added a new menu item to a menu and want to start another activity once the user clicks the menu item with id: plot. The intent will be sent from if… Read More MenuItem and toolbar missing in new activity Android Studio Unknown Bug