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I'm new to C#. I'm using .NET IdentityModel with AWS Cognito User Pools and attempting to get logout to work. CreateEndSessionUrl sets post_logout_redirect_uri but Cognito requires logout_uri. I'm attempting to use the extra parameter but getting a Parameter Count Mismatch.

Here is my code:

StringDictionary cognitoParameters = new StringDictionary();
cognitoParameters.Add("client_id", OAuthConfiguration.ClientId);
cognitoParameters.Add("logout_uri", OAuthConfiguration.EndsessionEndpointPath);

var endsessionEndpoint = OAuthConfiguration.Authority.TrimEnd('/') + "/" + OAuthConfiguration.EndsessionEndpointPath;
var requestUrl = new RequestUrl(endsessionEndpoint);
var endSessionUrl = requestUrl.CreateEndSessionUrl(
   idTokenHint: HttpContext.Current.GetToken(OidcConstants.ResponseTypes.IdToken),
   postLogoutRedirectUri: OAuthConfiguration.Host,
   state: null,
   extra: cognitoParameters
);

The CreateEndSessionUrl documentation says "The extra parameter can either be a string dictionary or an arbitrary other type with properties. In both cases the values will be serialized as keys/values." I assume I'm creating the string dictionary incorrectly somehow.

The error I get is:

Message: Parameter count mismatch.

Exception type: System.Reflection.TargetParameterCountException
Stack trace:
at System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture)
at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, Object[] index)
at IdentityModel.Internal.ValuesHelper.ObjectToDictionary(Object values)
at IdentityModel.Client.RequestUrlExtensions.CreateEndSessionUrl(RequestUrl request, String idTokenHint, String postLogoutRedirectUri, String state, Object extra)
at Indice.Kentico.Oidc.EndSessionOidcHandler.EndSession()
at Indice.Kentico.Oidc.EndSessionOidcHandler.ProcessRequest(HttpContext context)
at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

Can someone help me understand how to properly format and include the extra parameter? I actually don't need the idTokenHint, postLogoutRedirectUri, or state if they can be excluded.

Bubba
  • 71
  • 6

1 Answers1

0

I figured out that I needed to create a Dictionary instead of a StringDictionary:

IDictionary cognitoParameters = new Dictionary<string,string>() {
  { "client_id", OAuthConfiguration.ClientId },
  { "logout_uri", OAuthConfiguration.Host.TrimEnd('/') + "/SignOut.ashx" }
};

It is working now.

Bubba
  • 71
  • 6