Xamarin表单连接到ASMX Web服务

Question

我正在尝试创建一个从ASMX Webservice获取数据的Xamarin表单项目

这是我正在使用的代码

var httpClient = new HttpClient();

httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
httpClient.DefaultRequestHeaders.Add("SOAPAction", "http://mobile.xn--schller-golf-xjb.dk/WebServices/IndoorServices.asmx/IndoorBruttoGns");

string soapstr = string.Format(@"<?xml version=""1.0"" encoding=""utf-8""?>
    <soap:Envelope xmlns:xsi=""http://www.w3.org/2001/XMLSchema-instance"" xmlns:xsd=""http://www.w3.org/2001/XMLSchema"" xmlns:soap=""http://schemas.xmlsoap.org/soap/envelope/"">
        <soap:Body>
            < IndoorBruttoGns xmlns = ""http://mobile.xn--schller-golf-xjb.dk/WebServices"" />
        </soap:Body>
    </soap:Envelope>");

var response = httpClient.PostAsync("http://mobile.xn--schller-golf-xjb.dk/WebServices/IndoorServices.asmx/IndoorBruttoGns", new StringContent(soapstr, Encoding.UTF8, "application/json")).Result;
var content = response.Content.ReadAsStringAsync().Result;
return content;

Web服务不需要任何输入，但我收到500内部服务器错误，我知道Web服务有效，因为我使用$ .ajax从PhoneGap项目调用它