title: IdentityServer4: MissingMethodException: Method not found: Int64 IdentityModel.EpochTimeExtensions.ToEpochTime<System.DateTimeOffset>
body: <p>Hi i´m working on a identityserver4 and a spa client (angular) solution. So far it worked great, but after i added a new dependency IdentityServer4.AccessTokenValidation with minimal changes on the client side. i get the following error message in the spa browser at the call of sts/connect/authorize?.....:
  MissingMethodException: Method not found: Int64 IdentityModel.EpochTimeExtensions.ToEpochTime(System.DateTimeOffset). (the error message is also shown at the console of the identityServer)</p>
  
  <p>that´s the complete error message:</p>
  
  <pre><code>IdentityServer4.Services.DefaultTokenService+&lt;CreateIdentityTokenAsync&gt;d__7.MoveNext()
  System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start&lt;TStateMachine&gt;(ref TStateMachine stateMachine)
  IdentityServer4.Services.DefaultTokenService.CreateIdentityTokenAsync(TokenCreationRequest request)
  IdentityServer4.ResponseHandling.AuthorizeResponseGenerator+&lt;CreateImplicitFlowResponseAsync&gt;d__9.MoveNext()
  System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
  System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
  IdentityServer4.ResponseHandling.AuthorizeResponseGenerator+&lt;CreateResponseAsync&gt;d__6.MoveNext()
  System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
  System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
  IdentityServer4.Endpoints.AuthorizeEndpointBase+&lt;ProcessAuthorizeRequestAsync&gt;d__14.MoveNext()
  System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
  System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
  IdentityServer4.Endpoints.AuthorizeEndpoint+&lt;ProcessAsync&gt;d__1.MoveNext()
  System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
  System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
  IdentityServer4.Hosting.IdentityServerMiddleware+&lt;Invoke&gt;d__4.MoveNext()
  System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
  IdentityServer4.Hosting.IdentityServerMiddleware+&lt;Invoke&gt;d__4.MoveNext()
  System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
  System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
  Microsoft.AspNetCore.Authentication.AuthenticationMiddleware+&lt;Invoke&gt;d__6.MoveNext()
  System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
  System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
  Microsoft.AspNetCore.Cors.Infrastructure.CorsMiddleware+&lt;Invoke&gt;d__7.MoveNext()
  System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
  System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
  IdentityServer4.Hosting.BaseUrlMiddleware+&lt;Invoke&gt;d__3.MoveNext()
  System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
  System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
  Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware+&lt;Invoke&gt;d__7.MoveNext()
  </code></pre>
  
  <p>I looking for update versions of the used dependencys but there are no one.
  used Nuget packages: IdentityServer4.AspNetIdentity ver. 2.0.0, IdentityServer4.AccessTokenValidation ver. 2.3.0, Identity.Dapper.MySQL ver. 0.7.0</p>
  
  <p>Have someone a idea to solve the problem?</p>