private static async Task UploadFileInModel_WithHttpClientAsync() { string filePath = @"D:\Test\de.json"; using var form = new MultipartFormDataContent(); using var fileContent = new ByteArrayContent(await File.ReadAllBytesAsync(filePath)); fileContent.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/form-data"); form.Add(fileContent, "File", Path.GetFileName(filePath)); // this is the changed part form.Add(new StringContent("de.json"), "Name"); form.Add(new StringContent("json file"), "Description"); var httpClient = new HttpClient() { BaseAddress = new Uri("https://localhost:7075") }; var response = await httpClient.PostAsync($"/File/UploadFileWithModel", form); response.EnsureSuccessStatusCode(); var responseContent = await response.Content.ReadAsStringAsync(); Console.WriteLine("UploadFileInModel_WithHttpClientAsync response :" + responseContent); }