I just saw the following syntax in code: (int, string) testTwo

It seems to mimic a Tuple, but the return types are incompatible with a Tuple. Example:

Tuple<int, string> test = Test.Get(); // This doesn't work
(int, string) testTwo = Test.Get(); // This works

public static class Test
{
  public static (int, string) Get()
  {
    return (1, "2");
  }
}

Seems like you can name the params too, but this appears to be for readability only, e.g.:

public static (int foo, string bar) Get()

1. What is this syntax called?
2. What's the real world use case?

CodePudding user response：

There are two tuple types in the modern C#/.NET - "old" ones - series of Tuple classes and value tuples introduced in C# 7 which are syntactic sugar based on series of ValueTuple structs and there is no conversions between those two (though both can be deconstructed - var (i1, i2) = Tuple.Create(1,2); and var (i1, i2) = (1,2); both are a valid code).

Tuples vs System.Tuple

C# tuples, which are backed by System.ValueTuple types, are different from tuples that are represented by System.Tuple types. The main differences are as follows:

• System.ValueTuple types are value types. System.Tuple types are reference types.
• System.ValueTuple types are mutable. System.Tuple types are immutable.
• Data members of System.ValueTuple types are fields. Data members of System.Tuple types are properties.

CodePudding user response：

When creating a Tuple in parentheses it's a value type, specifically it's a System.ValueTuple. System.Tuple is a reference type.

CodePudding user response：

It's a Tuple type which maps to System.ValueTuple, a value type, available in .NET Core and Framework 4.7 .

A ValueTuple and a Tuple are distinct, incompatible types.

The syntax with parentheses is tuple assignment and deconstruction.