请帮助我。 如何从xaml.cs页面调用以下函数？ 在项目中添加了.asmx服务，

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    public System.Threading.Tasks.Task<GetuserService.GetUserauthentiResponse> GetUserauthentiAsync(string userid,string password)
    {
        GetuserService.GetUserauthentiRequest inValue = new GetuserService.GetUserauthentiRequest();
        inValue.Body = new GetuserService.GetUserauthentiRequestBody();
        inValue.Body.userid = userid;
        inValue.Body.password = password;
        return ((GetuserService.WebServiceDNNUserauth_4AndroidSoap)(this)).GetUserauthentiAsync(inValue);
    }