Dynamics CRM2016 解决C#调用web api报错无法显示错误详情的问题

    在js中调用web api如果报错，比如400 bad request,比如500都会在response中看到具体的错误，方便我们及时修正,但是在c#中通过httpwebrequest调用报错是看不到的,所以往往需要我们把url拷出来在浏览器里查看，甚至需要借助第三方工具来查看非get请求类的错误，还是比较麻烦的。
    先来看下普通的httprequest方式报错返回是什么样的，示例代码很简单，创建一条name为DTCC的account记录
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.
Create("http://121.40.75.24:5555/origin/api/data/v8.0/accounts");
req.Credentials = new NetworkCredential(username, pwd, domain);
req.Method = "post";
req.Accept = "application/json";
req.ContentType = "application/json; charset=utf-8";
byte[] data = Encoding.UTF8.GetBytes("{\"name\":\"DTCC\"}");
Stream newStream = req.GetRequestStream();
newStream.Write(data, 0, data.Length);
newStream.Close();
using (HttpWebResponse res = (HttpWebResponse)req.GetResponse())
{
StreamReader read = new StreamReader(res.GetResponseStream());
string result = read.ReadToEnd();
}       因为我写了个create的pre插件阻止了创建，所以这块提示是500错，但看不到具体的错误原因



    咱们来换一种方式，示例代码如下
public static async Task Demo_API_02()
{
HttpClientHandler sHandler = new HttpClientHandler();
sHandler.Credentials = new NetworkCredential(username, pwd, domain);
using (var client = new HttpClient(sHandler))
{
client.BaseAddress = new Uri("http://121.40.75.24:5555/origin/api/data/v8.0/accounts");
client.DefaultRequestHeaders.Accept.Clear();
HttpRequestMessage createRequest2 = new HttpRequestMessage(HttpMethod.Post, "");
client.DefaultRequestHeaders.Add("ContentType", "application/json; charset=utf-8");
client.DefaultRequestHeaders.Add("OData-MaxVersion", "4.0");
client.DefaultRequestHeaders.Add("OData-Version", "4.0");
createRequest2.Content = new StringContent("{\"name\":\"DTCC\"}", Encoding.UTF8, "application/json");
HttpResponseMessage createResponse2 = await client.SendAsync(createRequest2);

if (createResponse2.StatusCode == HttpStatusCode.NoContent)
{
var demoUri = createResponse2.Headers.GetValues("OData-EntityId").FirstOrDefault();
}
else
{
var exception = new CrmHttpResponseException(createResponse2.Content);
}
}
}  看下结果,准确的抓到了我插件中抛出的exception错


   示例代码中用到的CrmHttpResponseException类代码如下
public class CrmHttpResponseException : System.Exception
{
#region Properties
private static string _stackTrace;
/// <summary>
/// Gets a string representation of the immediate frames on the call stack.
/// </summary>
public override string StackTrace
{
get { return _stackTrace; }
}

#endregion Properties
#region Constructors
/// <summary>
/// Initializes a new instance of the CrmHttpResponseException class.
/// </summary>
/// <param name="content">The populated HTTP content in Json format.</param>

public CrmHttpResponseException(HttpContent content) : base(ExtractMessageFromContent(content)) { }

/// <summary>
/// Initializes a new instance of the CrmHttpResponseException class.
/// </summary>
/// <param name="content">The populated HTTP content in Json format.</param>
/// <param name="innerexception">The exception that is the cause of the current exception,or a null reference
/// if no innerexception is specified.</param>

public CrmHttpResponseException(HttpContent content, Exception innerexception) : base(ExtractMessageFromContent(content), innerexception) { }

#endregion Constructors
#region Methods
/// <summary>
/// Extracts the CRM specific error message and stack trace from an HTTP content.
/// </summary>
/// <param name="content">The HTTP content in Json format.</param>
/// <returns>The error message.</returns>

private static string ExtractMessageFromContent(HttpContent content)
{
string message = String.Empty;
string downloadedContent = content.ReadAsStringAsync().Result;
if (content.Headers.ContentType.MediaType.Equals("text/plain"))
{
message = downloadedContent;
}
else if (content.Headers.ContentType.MediaType.Equals("application/json"))
{
JObject jcontent = (JObject)JsonConvert.DeserializeObject(downloadedContent);
IDictionary<string, JToken> d = jcontent;

// An error message is returned in the content under the 'error' key.

if (d.ContainsKey("error"))
{
JObject error = (JObject)jcontent.Property("error").Value;
message = (String)error.Property("message").Value;
}
else if (d.ContainsKey("Message"))
message = (String)jcontent.Property("Message").Value;
if (d.ContainsKey("StackTrace"))
_stackTrace = (String)jcontent.Property("StackTrace").Value;
}
else if (content.Headers.ContentType.MediaType.Equals("text/html"))
{
message = "HTML content that was returned is shown below.";
message += "\n\n" + downloadedContent;
}
else
{
message = String.Format("No handler is available for content in the {0} format.", content.Headers.ContentType.MediaType.ToString());
}
return message;
#endregion Methods
}
}    最后感谢路人甲提供的参考代码。