API Import 400 Bad Request Error when uploading pbix file

Anonymous

I see you are appending the nameConflict parameter to the URL, one most probably reason I can think of for your 400 error is that the url with nameConflict parameter would throw error if the report you'd like to import doesn't already exist. 

https://api.powerbi.com/v1.0/myorg/imports?datasetDisplayName=TestImport&nameConflict=Overwrite

By the way, I don't find /groups/{groupid} in the URL. Do note the that you can only embed the reports from a created app workspace.

For better troubleshooting, I'd suggest you add an extra catch block.

catch (WebException wex)
            {
                if (wex.Response != null)
                {
                    using (var errorResponse = (HttpWebResponse)wex.Response)
                    {
                        using (var reader = new StreamReader(errorResponse.GetResponseStream()))
                        {
                            string errorString = reader.ReadToEnd();
                            dynamic respJson = JsonConvert.DeserializeObject<dynamic>(errorString);
                            Console.WriteLine(respJson.ToString());
                            //TODO: use JSON.net to parse this string and look at the error message
                        }
                    }
                }
            }

Also you can reference my import pbix file demo.

using System;
using System.Net;
//Install-Package Microsoft.IdentityModel.Clients.ActiveDirectory -Version 2.21.301221612
using Microsoft.IdentityModel.Clients.ActiveDirectory;

//Install-Package Newtonsoft.Json 
using Newtonsoft.Json;
using System.IO;
using System.Threading.Tasks;

namespace ConsoleApplication39
{

    class Program
    {

        //Step 1 - Replace {client id} with your client app ID. 
        //To learn how to get a client app ID, see Register a client app (https://msdn.microsoft.com/en-US/library/dn877542.aspx#clientID)
        private static string clientID = "{client id}";
          
        //Resource Uri for Power BI API
        private static string resourceUri = "https://analysis.windows.net/powerbi/api";

        //OAuth2 authority Uri
        private static string authorityUri = "https://login.windows.net/common/oauth2/authorize";
         
        private static string token = String.Empty;

        //Uri for Power BI datasets
        private static string pbiEndpoint = "https://api.powerbi.com/v1.0/myorg"; 

        //Example dataset name and group name 
        private static string groupId = "{group id}";

        static void Main(string[] args)
        {
            //Import sample 
            string pbixPath = @"C:\test\KPI.pbix";
            string datasetDisplayName = "mydataset";

            Task t = Import(string.Format("{0}/groups/{1}/imports?datasetDisplayName={2}&nameConflict=Overwrite", pbiEndpoint, groupId, datasetDisplayName), pbixPath);
            t.Wait();

            Console.ReadKey();

        }

        public static async Task<string> Import(string url, string fileName)
        {
            string responseStatusCode = string.Empty;

            string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
            byte[] boundarybytes = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");

            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);

            request.ContentType = "multipart/form-data; boundary=" + boundary;
            request.Method = "POST";
            request.KeepAlive = true;

            var credential = new UserCredential(yourPbiAccount, Password);

            // Authenticate using created credentials
            var authenticationContext = new AuthenticationContext(authorityUri);
            var authenticationResult = await authenticationContext.AcquireTokenAsync(resourceUri, clientID, credential);
            token = authenticationResult.AccessToken;


            request.Headers.Add("Authorization", String.Format("Bearer {0}", token.ToString()));

            using (Stream rs = request.GetRequestStream())
            {
                rs.Write(boundarybytes, 0, boundarybytes.Length);

                string headerTemplate = "Content-Disposition: form-data; filename=\"{0}\"\r\nContent-Type: application / octet - stream\r\n\r\n";
                string header = string.Format(headerTemplate, fileName);
                byte[] headerbytes = System.Text.Encoding.UTF8.GetBytes(header);
                rs.Write(headerbytes, 0, headerbytes.Length);

                using (FileStream fileStream = new FileStream(fileName, FileMode.Open, FileAccess.Read))
                {
                    byte[] buffer = new byte[4096];
                    int bytesRead = 0;
                    while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
                    {
                        rs.Write(buffer, 0, bytesRead);
                    }
                }

                byte[] trailer = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
                rs.Write(trailer, 0, trailer.Length);
            }
            try
           {
                using (HttpWebResponse response = request.GetResponse() as System.Net.HttpWebResponse)
                {
                    responseStatusCode = response.StatusCode.ToString();

                    Console.WriteLine("Import pbix file is {0}", responseStatusCode);
                }
            }
            catch (WebException wex)
            {
                if (wex.Response != null)
                {
                    using (var errorResponse = (HttpWebResponse)wex.Response)
                    {
                        using (var reader = new StreamReader(errorResponse.GetResponseStream()))
                        {
                            string errorString = reader.ReadToEnd();
                            dynamic respJson = JsonConvert.DeserializeObject<dynamic>(errorString);
                            Console.WriteLine(respJson.ToString());
                            //TODO: use JSON.net to parse this string and look at the error message
                        }
                    }
                }
            } 

            return responseStatusCode;
        }
         
    }
}