//Create Power of Attorney
var client = new BFSServiceReference.bfsapiSoapClient();

var credentials = new BFSServiceReference.Credentials()
{
    UserName = bfsusername, //Username of administrative user in your instance of BFS
    Password = bfspassword, //Password of the administrative user in your instance of BFS
};

var response = client.CreatePOAs(new BFSServiceReference.CreatePOARequest()
{
    Credentials = credentials,

    identify = bfsidentifier, //Identifier is a unique token for your instance of BFS    

    Entities = new[]
    {
        new POA()
        {
            AccountId = new Guid("987a7c34-bbfd-4a78-bfc7-fe9b7d738e86"),
            Key = "View",
            POACustomerNo = "10000180"             
        },
    }

});

foreach (var c in response.Entities)
{
    Console.WriteLine(c.BrickId + ", " + c.POACustomerNo);
}