I am starting to learn nullable types and ran into following behavior. While trying nullable int, i see comparison operator gives me unexpected result. For example, In my code below, The output i get is “both and 1 are equal”. Note, it does not print “null” as well. int? a = null; int? b = … Read more
PHP 7 introduces return type declarations. Which means I can now indicate the return value is a certain class, interface, array, callable or one of the newly hintable scalar types, as is possible for function parameters. function returnHello(): string { return ‘hello’; } Often it happens that a value is not always present, and that … Read more
If I have a nullable type Xyz?, I want to reference it or convert it to a non-nullable type Xyz. What is the idiomatic way of doing so in Kotlin? For example, this code is in error: val something: Xyz? = createPossiblyNullXyz() something.foo() // Error: “Only safe (?.) or non-null asserted (!!.) calls are allowed … Read more
I have an enum string name; public enum Color { Red, Green, Yellow } How to set it to NULL on load. name = “”; Color color = null; //error Edited: My bad, I didn’t explain it properly. But all the answers related to nullable is perfect. My situation is What if, I have get/set … Read more
Why does this not compile? int? number = true ? 5 : null; Type of conditional expression cannot be determined because there is no implicit conversion between ‘int’ and <null> 4 Answers 4
How do I check if a given object is nullable in other words how to implement the following method… bool IsNullableValueType(object o) { … } I am looking for nullable value types. I didn’t have reference types in mind. //Note: This is just a sample. The code has been simplified //to fit in a post. … Read more
This question already has answers here: How to check if an object is nullable? (14 answers) Closed 9 years ago. In order to check if a Type ( propertyType ) is nullable, I’m using: bool isNullable = “Nullable`1”.Equals(propertyType.Name) Is there some way that avoid using magic strings ? 2 Answers 2
There is paradox in the exception description: Nullable object must have a value (?!) This is the problem: I have a DateTimeExtended class, that has { DateTime? MyDataTime; int? otherdata; } and a constructor DateTimeExtended(DateTimeExtended myNewDT) { this.MyDateTime = myNewDT.MyDateTime.Value; this.otherdata = myNewDT.otherdata; } running this code DateTimeExtended res = new DateTimeExtended(oldDTE); throws an InvalidOperationException … Read more
This question already has answers here: Conditional operator assignment with Nullable<value> types? (6 answers) Why doesn’t this C# code compile? (4 answers) Closed 9 years ago. I just came across a weird error: private bool GetBoolValue() { //Do some logic and return true or false } Then, in another method, something like this: int? x … Read more
How can I convert the nullable DateTime dt2 to a formatted string? DateTime dt = DateTime.Now; Console.WriteLine(dt.ToString(“yyyy-MM-dd hh:mm:ss”)); //works DateTime? dt2 = DateTime.Now; Console.WriteLine(dt2.ToString(“yyyy-MM-dd hh:mm:ss”)); //gives following error: no overload to method ToString takes one argument 21 Answers 21
