ASP.NET Web Api返回对象类型为JSON还是XML

在Umbraco平台上开发过程中，我用WebApi返回JSON result给前端

前端使用React调用这个web api来获取JSON result

我写的web api方法是返回JSON 类型的string, 代码如下

[HttpGet]
[HttpQueryStringFilter("queryStrings")]
public string GetPDFSearchResults(FormDataCollection queryStrings)
{
string product = queryStrings.HasKey("product") ? queryStrings.GetValue<string>("product") : "0003";
string category = queryStrings.HasKey("category") ? queryStrings.GetValue<string>("category") : "0002";
string docType = queryStrings.HasKey("docType") ? queryStrings.GetValue<string>("docType") : "0001";
string terms = queryStrings.HasKey("search") ? queryStrings.GetValue<string>("search") : string.Empty;
var jsonError = JsonHelper.PDFJsonError();
HttpResponseMessage resp = new HttpResponseMessage();
resp.Content = new StringContent(jsonError, System.Text.Encoding.UTF8, "application/json");
if (!string.IsNullOrEmpty(terms))
{

var results = Umbraco.PerformContentSearch(terms, product, category, docType);

//var jsonResult = JsonConvert.SerializeObject(results);
var jsonResult = "";
foreach (PDFSearchResult mapResult in results)
{

var docTypeJson = JsonHelper.getJsonByObject(mapResult.DocumentType);
docTypeJson = docTypeJson.TrimStart('[').TrimEnd(']');
docTypeJson = docTypeJson.Replace(@"\/", "/");
var categoryJson = JsonHelper.getJsonByObject(mapResult.Category);
categoryJson = categoryJson.TrimStart('[').TrimEnd(']');
var productJson = JsonHelper.getJsonByObject(mapResult.Product);
productJson = productJson.TrimStart('[').TrimEnd(']');

jsonResult += "{\"id\":" + mapResult.Id + ",";
jsonResult += "\"approvalStatus\":\"" + mapResult.ApprovalStatus + "\",";
jsonResult += "\"score\":\"" + mapResult.Score + "\",";
jsonResult += "\"title\":\"" + mapResult.Title + "\",";
jsonResult += "\"file_name\":\"" + mapResult.pdfName + "\",";
jsonResult += "\"url\":\"" + mapResult.FileUrl + "\",";
jsonResult += "\"create_date\":\"" + mapResult.CreateDate + "\",";
jsonResult += "\"update_date\":\"" + mapResult.UpdateDate + "\",";

jsonResult += JsonHelper.GetConditionJson(docTypeJson, categoryJson, productJson) + "},";
}

jsonResult = jsonResult.TrimEnd(',');

return jsonResult

//return Json(searchResults, JsonRequestBehavior.AllowGet);

}
else
{
return "Search term not found"
//return Json("Search term not found", JsonRequestBehavior.AllowGet);

}

}

但在Chrome客户端调用这个web api时，发现它返回的是

<string xmlns="http://schemas.microsoft.com/2003/10/Serialization/">
{"company":"Aus 7-11 Mobil Australia","customer":"ECL Group Australia Pty Ltd","dispatch_date":"2015-02-12","has_warranty":false,"serial_number":"1401410","site":"2273 West Ryde","warranty_date":""}
</string>

或者在IE上返回的是

"{\"company\":\"Aus 7-11 Mobil Australia\",\"customer\":\"ECL Group Australia Pty Ltd\",\"dispatch_date\":\"2015-02-12\",\"has_warranty\":false,\"serial_number\":\"1401410\",\"site\":\"2273 West Ryde\",\"warranty_date\":\"\"}"

而我实际需要的返回结果是

{"company":"Aus 7-11 Mobil Australia","customer":"ECL Group Australia Pty Ltd","dispatch_date":"2015-02-12","has_warranty":false,"serial_number":"1401410","site":"2273 West Ryde","warranty_date":""}

如何解决呢

在读了这篇文章 http://www.luckyonecn.com/blog/fix_content-type_to_Applicationjson_in_WebApi/ 后，

我对代码进行了改写，返回HttpResponseMessage, 限定返回的ContentType 为application/json, 改写后代码如下

[HttpGet]
[HttpQueryStringFilter("queryString")]
public HttpResponseMessage GetWarrantySearchResult(FormDataCollection queryString)
{
string serialNum = queryString.HasKey("search") ? queryString.GetValue<string>("search").Trim() : string.Empty;
var jsonError = JsonHelper.WarrantyJsonError();
HttpResponseMessage resp = new HttpResponseMessage();
resp.Content = new StringContent(jsonError, System.Text.Encoding.UTF8, "application/json");
if (!string.IsNullOrEmpty(serialNum))
{
try
{

//Send SOAP Request
WebRequest webRequest = WebRequest.Create("http://gglnzdom1/pec/product.nsf/getWarranty?WSDL");
HttpWebRequest httpRequest = (HttpWebRequest)webRequest;
httpRequest.Method = "POST";
httpRequest.ContentType = "text/xml; charset=utf-8";
httpRequest.ProtocolVersion = HttpVersion.Version11;
httpRequest.Credentials = CredentialCache.DefaultCredentials;
Stream requestStream = httpRequest.GetRequestStream();
//Create Stream and Complete Request
StreamWriter streamWriter = new StreamWriter(requestStream, Encoding.ASCII);

string soapRequest = "<soapenv:Envelope xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xsd='http://www.w3.org/2001/XMLSchema' xmlns:soapenv='http://schemas.xmlsoap.org/soap/envelope/' xmlns:urn='urn:DefaultNamespace'><soapenv:Header/><soapenv:Body><urn:GETWARRANTYARRAY soapenv:encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'><SERIAL xsi:type='xsd:string'>" + serialNum + "</SERIAL></urn:GETWARRANTYARRAY></soapenv:Body></soapenv:Envelope>";
streamWriter.Write(soapRequest.ToString());
streamWriter.Close();

//Get SOAP response
HttpWebResponse wr = (HttpWebResponse)httpRequest.GetResponse();

StreamReader srd = new StreamReader(wr.GetResponseStream());
string resultXmlFromWebService = srd.ReadToEnd();

if (resultXmlFromWebService.Contains("Serial Number not found</OILCOMPANY>"))
{
return resp;

}
else if (resultXmlFromWebService.Contains("<faultstring>"))
{
return resp;

}
else
{
var resultXml = resultXmlFromWebService.Replace(" xsi:type=\"xsd:string\"", "");

var warrantyInfo = resultXml.Substring(resultXml.IndexOf("<WARRANTY>") + 10, resultXml.IndexOf("</WARRANTY>") - (resultXml.IndexOf("<WARRANTY>") + 10));
bool hasWarranty = false;
DateTime warrantyDate;
var warrantyDateStr = "";
if (DateTime.TryParse(warrantyInfo, out warrantyDate))
{
hasWarranty = true;

}
if (hasWarranty)
warrantyDateStr = UmbracoFuelHelper.FormatDateString(warrantyInfo);

var warrantyResult = new WarrantySearchResult()
{
SerialNumber = serialNum,
Company = resultXml.Substring(resultXml.IndexOf("<OILCOMPANY>") + 12, resultXml.IndexOf("</OILCOMPANY>") - (resultXml.IndexOf("<OILCOMPANY>") + 12)) + " " + resultXml.Substring(resultXml.IndexOf("<COUNTRY>") + 9, resultXml.IndexOf("</COUNTRY>") - (resultXml.IndexOf("<COUNTRY>") + 9)),
Site = resultXml.Substring(resultXml.IndexOf("<SITE>") + 6, resultXml.IndexOf("</SITE>") - (resultXml.IndexOf("<SITE>") + 6)),
Customer = resultXml.Substring(resultXml.IndexOf("<CUSTOMER>") + 10, resultXml.IndexOf("</CUSTOMER>") - (resultXml.IndexOf("<CUSTOMER>") + 10)),
DespatchDate = UmbracoFuelHelper.FormatDateString(resultXml.Substring(resultXml.IndexOf("<DESPATCHED>") + 12, resultXml.IndexOf("</DESPATCHED>") - (resultXml.IndexOf("<DESPATCHED>") + 12))),
HasWarranty = hasWarranty,
WarrantyDate = warrantyDateStr

};

var jsonWarranty = JsonHelper.getJsonByObject(warrantyResult);

resp.Content = new StringContent(jsonWarranty, System.Text.Encoding.UTF8, "application/json");

return resp;

//return JsonConvert.SerializeObject(jsonWarranty);

}
}
catch (Exception ex)
{
throw ex;
}

}
else
{
return resp;
}

}

现在返回的就是JSON

{"company":"Aus 7-11 Mobil Australia","customer":"ECL Group Australia Pty Ltd","dispatch_date":"2015-02-12","has_warranty":false,"serial_number":"1401410","site":"2273 West Ryde","warranty_date":""}