Error Found : System.ArgumentException: An item with the same key has already been added. Key: System.Net.Http.Headers.HeaderDescriptor at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior) at AdsPortalClientApi.ApiClient.addHeaders(Boolean bAddHeader) in F:\Development\AdsPortal\AdsPortalClientApi\ApiClient.cs:line 90 at AdsPortalClientApi.ApiClient.GetAsync[T](Uri requestUrl) in F:\Development\AdsPortal\AdsPortalClientApi\ApiClient.cs:line 34 at AdsPortalClientApi.ApiClient.GetProduct(Int32 iProductId) in F:\Development\AdsPortal\AdsPortalClientApi\ProductClient.cs:line 77 at AdsPortals.ProductController.DetailProduct(Int32 id) in F:\Development\AdsPortal\AdsPortal\Controllers\ProductController.cs:line 43