C# Language C# 6.0 Features Index initializers
Example
Index initializers make it possible to create and initialize objects with indexes at the same time.
This makes initializing Dictionaries very easy:
var dict = new Dictionary<string, int>()
{
["foo"] = 34,
["bar"] = 42
};
Any object that has an indexed getter or setter can be used with this syntax:
class Program
{
public class MyClassWithIndexer
{
public int this[string index]
{
set
{
Console.WriteLine($"Index: {index}, value: {value}");
}
}
}
public static void Main()
{
var x = new MyClassWithIndexer()
{
["foo"] = 34,
["bar"] = 42
};
Console.ReadKey();
}
}
Output:
Index: foo, value: 34
Index: bar, value: 42
If the class has multiple indexers it is possible to assign them all in a single group of statements:
class Program
{
public class MyClassWithIndexer
{
public int this[string index]
{
set
{
Console.WriteLine($"Index: {index}, value: {value}");
}
}
public string this[int index]
{
set
{
Console.WriteLine($"Index: {index}, value: {value}");
}
}
}
public static void Main()
{
var x = new MyClassWithIndexer()
{
["foo"] = 34,
["bar"] = 42,
[10] = "Ten",
[42] = "Meaning of life"
};
}
}
Output:
Index: foo, value: 34
Index: bar, value: 42
Index: 10, value: Ten
Index: 42, value: Meaning of life
It should be noted that the indexer set accessor might behave differently compared to an Add method (used in collection initializers).
For example:
var d = new Dictionary<string, int>
{
["foo"] = 34,
["foo"] = 42,
}; // does not throw, second value overwrites the first one
versus:
var d = new Dictionary<string, int>
{
{ "foo", 34 },
{ "foo", 42 },
}; // run-time ArgumentException: An item with the same key has already been added.
