Many languages allow you to extract values from objects into variables. C# 7.0 introduces a new syntax for this called deconstruction which is similar to destructuring in other languages.

Only tuples ^{C# 7.0} are deconstructed automatically. Other types need a Deconstruct method with out parameters, defined either directly on the type or as an extension method ^{C# 3.0}. Some .NET types such as KeyValuePair<TKey, TValue> and DictionaryEntry already provide one.

Code

Now

void ProcessShipment(Shipment shipment)
{
    var (tracking, country, postCode) = shipment;

    // ...
}

class Shipment
{
    public string Tracking { get; set; }
    public string Country { get; set; }
    public string PostCode { get; set; }

    public void Deconstruct(out string tracking, out string country, out string postCode)
    {
        tracking = Tracking;
        country = Country;
        postCode = PostCode;
    }
}

Before

void ProcessShipment(Shipment shipment)
{
    var tracking = shipment.Tracking;
    var country = shipment.Country;
    var postCode = shipment.PostCode;

    // ...
}

Notes

• You can either:
  • Use the var keyword to infer all the types from the deconstruction
  • Declare the types inline with the deconstruction individually (string tracking, string country, var postCode) = shipment;
  • Assign the values directly to existing variables (tracking, country, postCode) = shipment;
• Use discards ^{C# 7.0} for values you don't need, e.g. var (_, country, _) = shipment;
• Declaration and assignment can be mixed in the same deconstruction from C# 10.0
• Records ^{C# 9.0} with positional parameters generate a Deconstruct method for you

More information

• Deconstructing tuples and other types
• Playing with C# 7 Deconstruct @ Adam Storr
• Tuple deconstruction in C# 7 @ Thomas Levesque