Common Mistakes with Named Parameters
When using named parameters, you must specify the positional parameters first. After that, the named parameters can exist in any order because they're preceded by the name of the field or property. The following, for example, will result in a compiler error: -
// This is an error because positional parameters can't follow // named parameters. [RegistryKey(Hive=RegistryHives.HKEY_LOCAL_MACHINE, "Foo")]
Additionally, you can't name positional parameters. When the compiler is compiling an attribute's usage, it will attempt to resolve the named parameters first. Then it will attempt to resolve what's left over-the positional parameters-with the method signature. The following will not compile because the compiler can resolve each named parameter but, when finished with the named parameters, it can't find any positional parameters and states that " No overload for method 'RegistryKeyAttribute' takes '0'' arguments ": -
[RegistryKey(ValueName="Foo", Hive=RegistryHives.HKEY_LOCAL_MACHINE)]
Lastly, named parameters can be any publicly accessible field or property-including a setter method-that is not static or const.