If you don’t like having to write the Deconstruct method, especially if you only need it in one place, here’s how to do it as a one-liner with LINQ: Using your original dictionary: var dic = new Dictionary<string, int>{ [“Bob”] = 32, [“Alice”] = 17 }; You can do it like this: foreach (var (name, … Read more
What do you mean by natively? C# 7 has a new feature that lets you return more than one value from a method thanks to tuple types and tuple literals. Take the following function for instance: (string, string, string) MyCoolFunction() // tuple return type { //… return (firstValue, secondValue, thirdValue); } Which can be used … Read more
It turns out not only tuples can be deconstructed but any type which has Deconstruct static (or extension) method with matching signature. Doing deconstruction correctly for IEnumerable is not trivial (see library suggested by David Arno in this answer), so let’s see how it works with simple IList instead (implementation is irrelevant, this one is … Read more
Inside a pattern matching switch statement using a case for an explicit type is asking if the value in question is of that specific type, or a derived type. It’s the exact equivalent of is switch (someString) { case string s: } if (someString is string) The value null does not have a type and … Read more
As you have observed, for: var list = new List<(int,int)>(); One would at least expect to be able to do the following: list.Select((x,y) => x*2 + y/2); But the C# 7 compiler doesn’t (yet) support this. It is also reasonable to desire sugar that would allow the following: void Foo(int x, int y) => … … Read more
Discards, in C#7 can be used wherever a variable is declared, to – as the name suggests – discard the result. So a discard can be used with out variables: p.GetCoordinates(out var x, out _); and it can be used to discard an expression result: _ = 42; In the example, p.GetCoordinates(out var x, out … Read more
ok this feels completely wrong but I cut <dependentAssembly> <assemblyIdentity name=”System.ValueTuple” publicKeyToken=”cc7b13ffcd2ddd51″ culture=”neutral” /> <bindingRedirect oldVersion=”0.0.0.0-4.0.3.0″ newVersion=”4.0.3.0″ /> </dependentAssembly> This out of my web.config for the main application. I was really just seeing what happened to see if there was an underlying dependency or something, not expecting it to run. It just carried on working, … Read more
As this answer is causing some confusion amongst some folk here, I should clarify that – as per the question – all references to “tuple” here refer to the ValueTuple type and new tuple syntactic sugar features of C# 7 and in no way refer to the old System.Tuple reference types. So now I am … Read more
A new feature in C# 6.0 allows to declare variable inside TryParse method. Declaration expressions was cut from C# 6.0 and wasn’t shipped in the final release. You currently can’t do that. There is a proposal for it on GitHub for C# 7 (also see this for future reference). Update (07/03/2017) With the official release … Read more
This is C# 7.0 which supports local functions…. public static IEnumerable<TSource> DistinctBy<TSource, TKey>( this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer) { if (source == null) throw new ArgumentNullException(nameof(source)); if (keySelector == null) throw new ArgumentNullException(nameof(keySelector)); // This is basically executing _LocalFunction() return _LocalFunction(); // This is a new inline method, // return within this … Read more