Dictionaries

Dictionary fields

A field, an element in a sequence, or a value in another dictionary with a dictionary type is mapped to an IDictionary<TKey, TValue>.

TKey resp. TValue is the mapped C# type for the Ice key type resp. value type. For example:

dictionary<string, double> StringDoubleDict;
dictionary<int, StringDoubleDict> DictOfDict;
dictionary<string, Value> StringValueDict;

struct DictionaryExample
{
    DictOfDict x;
    StringValueDict y;
}

maps to:

public partial record struct DictionaryExample
{
    public required IDictionary<int, IDictionary<string, double>> X { get; set; }

    public required IDictionary<string, IceClass?> Y { get; set; }
}

By default, when the generated code decodes a dictionary, it creates a C# Dictionary<TKey, TValue> that is transmitted to you (the application) as an IDictionary<TKey, TValue>. You can safely cast this IDictionary<TKey, TValue> to a Dictionary<TKey, TValue> after decoding.

You can override this default with the "cs:generic" metadata directive described below. This directive only changes the type that the generated code uses during decoding to fill-in the field: the C# field type itself remains an IDictionary<TKey, TValue>.

Dictionary parameters and return values

A dictionary parameter has one mapping when it's sent and a different mapping when it's received. This distinction between incoming and outgoing values makes sending dictionaries more convenient and occasionally faster.

You can override the default mapping for incoming values with the "cs:generic" metadata directive (see below). This gives you the C# type you specified for incoming values. "cs:generic" doesn't change the mapping for outgoing values.

cs:generic metadata

You can use the "cs:generic" metadata directive to customize the mapping of your dictionary. This attribute accepts a single string argument: "SortedDictionary" or "SortedList".

For example:

["cs:generic:SortedDictionary"]
dictionary<long, Employee> EmployeeMap;