Error Found : System.InvalidOperationException: Operations that change non-concurrent collections must have exclusive access. A concurrent update was performed on this collection and corrupted its state. The collection's state is no longer correct. at System.Collections.Generic.Dictionary`2.Remove(TKey key) 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 79 at AdsPortals.ProductController.DetailProduct(Int32 id) in F:\Development\AdsPortal\AdsPortal\Controllers\ProductController.cs:line 57