Why do I need "field:" in my attribute declaration "[field:NonSerialized]"?

Question

I can't find "field" listed as a C# keyword anywhere. Does anyone know the background on this?

Answer 1

This is necessary, for example, if you are marking an event as non-serializable. It specifies the target that the attribute applies to.

It is part of the attribute target syntax. From the specification:

attribute-target:
    field
    event
    method
    param
    property
    return
    type

See also the documentation for NonSerializedAttribute:

To apply the NonSerializedAttribute class to an event, set the attribute location to field, as shown in the following C# code.

[field:NonSerializedAttribute()]

public event ChangedEventHandler Changed;