There are two types of nullable – Nullable<T> and reference-type. Jon has corrected me that it is hard to get type if boxed, but you can with generics: – so how about below. This is actually testing type T, but using the obj parameter purely for generic type inference (to make it easy to call) … Read more
Absolutely – use Nullable.GetUnderlyingType: if (Nullable.GetUnderlyingType(propertyType) != null) { // It’s nullable } Note that this uses the non-generic static class System.Nullable rather than the generic struct Nullable<T>. Also note that that will check whether it represents a specific (closed) nullable value type… it won’t work if you use it on a generic type, e.g. … Read more
You should change the line this.MyDateTime = myNewDT.MyDateTime.Value; to just this.MyDateTime = myNewDT.MyDateTime; The exception you were receiving was thrown in the .Value property of the Nullable DateTime, as it is required to return a DateTime (since that’s what the contract for .Value states), but it can’t do so because there’s no DateTime to return, … Read more
The compiler first tries to evaluate the right-hand expression: GetBoolValue() ? 10 : null The 10 is an int literal (not int?) and null is, well, null. There’s no implicit conversion between those two hence the error message. If you change the right-hand expression to one of the following then it compiles because there is … Read more
Console.WriteLine(dt2 != null ? dt2.Value.ToString(“yyyy-MM-dd hh:mm:ss”) : “n/a”); EDIT: As stated in other comments, check that there is a non-null value. Update: as recommended in the comments, extension method: public static string ToString(this DateTime? dt, string format) => dt == null ? “n/a” : ((DateTime)dt).ToString(format); And starting in C# 6, you can use the null-conditional … Read more
I think a lot of people concentrate on the fact that this value is nullable, and don’t think about what they actually want 🙂 bool? nullableBool = true; if (nullableBool == true) { … } // true else { … } // false or null Or if you want more options… bool? nullableBool = true; … Read more
Laravel 5 now supports changing a column; here’s an example from the offical documentation: Schema::table(‘users’, function($table) { $table->string(‘name’, 50)->nullable()->change(); }); Source: http://laravel.com/docs/5.0/schema#changing-columns Laravel 4 does not support modifying columns, so you’ll need use another technique such as writing a raw SQL command. For example: // getting Laravel App Instance $app = app(); // getting laravel … Read more
int.TryParse is probably a tad easier: public static int? ToNullableInt(this string s) { int i; if (int.TryParse(s, out i)) return i; return null; } Edit @Glenn int.TryParse is “built into the framework”. It and int.Parse are the way to parse strings to ints.
Clearly the machine code the JIT compiler can generate for the first case is much more efficient. One rule that really helps there is that an object can only be unboxed to a variable that has the same type as the boxed value. That allows the JIT compiler to generate very efficient code, no value … Read more
Of course, people will do what they want. But we did have a clear intention when adding this feature, and it was not to be a general purpose Maybe type, as much as many people would have liked us to do so. Our intention was to provide a limited mechanism for library method return types … Read more