Search code examples
c#httpclientsharepoint-onlinesharepoint-api

Sharepoint online API returns: HTTP Error 400. A request header field is too long

I have a loop that will loop through records in my DB, pulling information i need and then creating 3 folders & upload a file.

This works OK for like 40 records but then it starts erroring out with the below response back from sharepoint: <!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01//EN\"\"http://www.w3.org/TR/html4/strict.dtd\">\r\n<HTML><HEAD><TITLE>Bad Request</TITLE>\r\n<META HTTP-EQUIV=\"Content-Type\" Content=\"text/html; charset=us-ascii\"></HEAD>\r\n<BODY><h2>Bad Request - Header Field Too Long</h2>\r\n<hr><p>HTTP Error 400. A request header field is too long.</p>\r\n</BODY></HTML>

I am not sure whats going on, i read online its todo with cookies but i am using HTTPClient to send the request so i dont know how that would effect it? I also seen onlne about changing the kestrel?

Can anybody shed some light on this for me? Provide me with an easy but working solution? I dont use CSOM for integrating to sharepoint online, i use HTTP Requests, below is a sample of how i interact with sharepoint.

It seems as if i get blocked or banned temporarily cause if i wait a good bit, i can then make the same request that failed previously, and it will work! So strange.

Sample code (Used to create a resource at Sharepoint):

//Set Endpoint
var sharePointEndpoint = $"https://{hostname}/sites/{site}/_api/web/folders";

//Set default headers
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", sharePointToken); //Set token
client.DefaultRequestHeaders.Add("Accept", "application/json;odata=verbose");

//Pre-Body data setup
var metaData = new MetaDataModel();
metaData.type = "SP.Folder";

//Body data setup
var bodyModel = new ExpandoObject() as IDictionary<string, object>;
bodyModel.Add("__metadata", metaData);
bodyModel.Add("ServerRelativeUrl", location + "/" + directoryName + "/");

//Set content headers
HttpContent strContent = new StringContent(JsonConvert.SerializeObject(bodyModel));
strContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");
strContent.Headers.ContentType.Parameters.Add(new NameValueHeaderValue("odata", "verbose"));

// Send request, grab response
var response = await client.PostAsync(sharePointEndpoint, strContent);

//Return response message
return response;
Solution

  • It turns out I needed to use Content-Length header when sending the request, once done I was able to successfully communicate with sharepoint without encountering this error.

    More information here: https://social.technet.microsoft.com/Forums/en-US/26459f1c-945d-4112-9200-69c5a33a37ff/sharepoint-online-rest-api-returns-http-error-400-a-request-header-field-is-too-long?forum=sharepointdevelopment

    Thanks.