ExchangeCredentials   - преобразование (NetworkCredential to ExchangeCredentials)

Performs an implicit conversion from NetworkCredential to ExchangeCredentials. This allows a NetworkCredential object to be implictly converted to an ExchangeCredential which is useful when setting credentials on an ExchangeService.

public static implicit operator ExchangeCredentials (
	NetworkCredential credentials
)

Public Shared Widening Operator CType ( 
	credentials As NetworkCredential
) As ExchangeCredentials

static implicit operator ExchangeCredentials^ (
	NetworkCredential^ credentials
)

F# не поддерживает объявление новых операторов приведения.

service.Credentials = new NetworkCredential("username","password");

service.Credentials = new WebCredentials(new NetworkCredential("username","password"));