"Formatted String Interpolation"

static void Test() {
	var percentageComplete = 12.345d;
	Console.WriteLine($"Percentage complete: {percentageComplete:F0}%"); // Prints "Percentage complete: 12%"
	Console.WriteLine($"Percentage complete: {percentageComplete:F2}%"); // Prints "Percentage complete: 12.34%"
}


Code snippet taken from "Two Decades of C#: A Reference - C# 5 and C# 6".