ارور No such host is known

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System.AggregateException: One or more errors occurred. (No such host is known) ---> System.Net.Http.HttpRequestException: No such host is known ---> System.Net.Sockets.SocketException: No such host is known at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken) --- End of inner exception stack trace --- at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken) at System.Threading.Tasks.ValueTask`1.get_Result() at System.Net.Http.HttpConnectionPool.CreateConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken) at System.Threading.Tasks.ValueTask`1.get_Result() at System.Net.Http.HttpConnectionPool.WaitForCreatedConnectionAsync(ValueTask`1 creationTask) at System.Threading.Tasks.ValueTask`1.get_Result() at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken) at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) at System.Net.Http.HttpClient.FinishSendAsyncBuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts) at Zarinpal.Payment.Verification(String authority) --- End of inner exception stack trace --- at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification) at TattoLearn.Web.Controllers.HomeController.<>c__DisplayClass7_0.<dowork>b__0() in E:\TattoLearn\TattoLearn.Web\Controllers\HomeController.cs:line 50 at System.Threading.Tasks.Task`1.InnerInvoke() at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) --- End of stack trace from previous location where exception was thrown --- at System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot) --- End of stack trace from previous location where exception was thrown --- at TattoLearn.Web.Controllers.HomeController.onlinePayment(Int32 id) in E:\TattoLearn\TattoLearn.Web\Controllers\HomeController.cs:line 74 at Microsoft.AspNetCore.Mvc.Internal.ActionMethodExecutor.TaskOfIActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments) at System.Threading.Tasks.ValueTask`1.get_Result() at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeActionMethodAsync() at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeNextActionFilterAsync() at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ActionExecutedContext context) at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeInnerFilterAsync() at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResourceFilter() at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context) at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted) at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeFilterPipelineAsync() at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeAsync() at Microsoft.AspNetCore.Builder.RouterMiddleware.Invoke(HttpContext httpContext) at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context) at Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context) at Elmah.Io.AspNetCore.ElmahIoMiddleware.Invoke(HttpContext context) ---> (Inner Exception #0) System.Net.Http.HttpRequestException: No such host is known ---> System.Net.Sockets.SocketException: No such host is known at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken) --- End of inner exception stack trace --- at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken) at System.Threading.Tasks.ValueTask`1.get_Result() at System.Net.Http.HttpConnectionPool.CreateConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken) at System.Threading.Tasks.ValueTask`1.get_Result() at System.Net.Http.HttpConnectionPool.WaitForCreatedConnectionAsync(ValueTask`1 creationTask) at System.Threading.Tasks.ValueTask`1.get_Result() at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken) at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) at System.Net.Http.HttpClient.FinishSendAsyncBuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts) at Zarinpal.Payment.Verification(String authority)<---