AWS SDK for .NET Documentation
ReleaseAddress Method (request)
AmazonAmazon.EC2AmazonEC2ClientReleaseAddress(ReleaseAddressRequest) Did this page help you?   Yes   No    Tell us about it...
Releases an elastic IP address associated with your account.
Declaration Syntax
C#
public ReleaseAddressResponse ReleaseAddress(
	ReleaseAddressRequest request
)
Parameters
request (ReleaseAddressRequest)
Release Address request
Return Value
Release Address Response from the service
Remarks
If you run this operation on an elastic IP address that is already released, the address might be assigned to another account which will cause Amazon EC2 to return an error. Releasing an IP address automatically disassociates it from any instance with which it is associated. To disassociate an IP address without releasing it, use the DisassociateAddress operation. After releasing an elastic IP address, it is released to the IP // address pool and might no longer be available to your account. Make sure to update your DNS records and any servers or devices that communicate with the address.
Exceptions

Assembly: AWSSDK (Module: AWSSDK) Version: 1.5.60.0 (1.5.60.0)