Error When Return EntityCollection in Output Parameter CRM

I create custom action in my Dynamics CRM I add input and output parameter, So the Case is when Input is send it will filter some entity with that attribute and return Entity Collection in my output parameter. But the problem is it will always return error with status 500 Internal Server Error, here is the complete error that I received

{
    "error": {
        "code": "0x80040216",
        "message": "System.Runtime.Serialization.SerializationException: Element 'schemas.microsoft.com/.../Contracts:Entity' contains data from a type that maps to the name 'CrmEarlyBound:BookableResourceBooking'. The deserializer has no knowledge of any type that maps to this name. Consider changing the implementation of the ResolveName method on your DataContractResolver to return a non-null value for name 'BookableResourceBooking' and namespace 'CrmEarlyBound'.\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract& dataContract)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Int32 id, RuntimeTypeHandle declaredTypeHandle, String name, String ns)\r\n   at ReadArrayOfEntityFromXml(XmlReaderDelegator , XmlObjectSerializerReadContext , XmlDictionaryString , XmlDictionaryString , CollectionDataContract )\r\n   at System.Runtime.Serialization.CollectionDataContract.ReadXmlValue(XmlReaderDelegator xmlReader, XmlObjectSerializerReadContext context)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract& dataContract)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Int32 id, RuntimeTypeHandle declaredTypeHandle, String name, String ns)\r\n   at ReadEntityCollectionFromXml(XmlReaderDelegator , XmlObjectSerializerReadContext , XmlDictionaryString[] , XmlDictionaryString[] )\r\n   at System.Runtime.Serialization.ClassDataContract.ReadXmlValue(XmlReaderDelegator xmlReader, XmlObjectSerializerReadContext context)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract& dataContract)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Int32 id, RuntimeTypeHandle declaredTypeHandle, String name, String ns)\r\n   at ReadKeyValuePairOfstringanyTypeFromXml(XmlReaderDelegator , XmlObjectSerializerReadContext , XmlDictionaryString[] , XmlDictionaryString[] )\r\n   at System.Runtime.Serialization.ClassDataContract.ReadXmlValue(XmlReaderDelegator xmlReader, XmlObjectSerializerReadContext context)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract& dataContract)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Int32 id, RuntimeTypeHandle declaredTypeHandle, String name, String ns)\r\n   at ReadParameterCollectionFromXml(XmlReaderDelegator , XmlObjectSerializerReadContext , XmlDictionaryString , XmlDictionaryString , CollectionDataContract )\r\n   at System.Runtime.Serialization.CollectionDataContract.ReadXmlValue(XmlReaderDelegator xmlReader, XmlObjectSerializerReadContext context)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract& dataContract)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Type declaredType, DataContract dataContract, String name, String ns)\r\n   at System.Runtime.Serialization.DataContractSerializer.InternalReadObject(XmlReaderDelegator xmlReader, Boolean verifyObjectName, DataContractResolver dataContractResolver)\r\n   at System.Runtime.Serialization.XmlObjectSerializer.ReadObjectHandleExceptions(XmlReaderDelegator reader, Boolean verifyObjectName, DataContractResolver dataContractResolver)\r\n   at System.Runtime.Serialization.XmlObjectSerializer.ReadObject(XmlDictionaryReader reader)\r\n   at Microsoft.Crm.Sandbox.SandboxUtility.DeserializeDataContract[T](Byte[] serializedDataContract, Assembly proxyTypesAssembly)\r\n   at Microsoft.Crm.Sandbox.SandboxExecutionContext.Merge(IExecutionContext originalContext)\r\n   at Microsoft.Crm.Sandbox.SandboxCodeUnit.ExecuteInternal(SandboxClient client, IExecutionContext context, SandboxTraceContext sandboxTraceContext, SandboxCallTracker callTracker, Guid parentExecutionId, String assemblyContents, Boolean& isSafeToRetry, Boolean& executeDone)\r\n   at Microsoft.Crm.Sandbox.SandboxCodeUnit.<>c__DisplayClass24_0.<Execute>b__0(): Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #BBF0AE79",
        "innererror": {
            "message": "System.Runtime.Serialization.SerializationException: Element 'schemas.microsoft.com/.../Contracts:Entity' contains data from a type that maps to the name 'CrmEarlyBound:BookableResourceBooking'. The deserializer has no knowledge of any type that maps to this name. Consider changing the implementation of the ResolveName method on your DataContractResolver to return a non-null value for name 'BookableResourceBooking' and namespace 'CrmEarlyBound'.\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract& dataContract)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Int32 id, RuntimeTypeHandle declaredTypeHandle, String name, String ns)\r\n   at ReadArrayOfEntityFromXml(XmlReaderDelegator , XmlObjectSerializerReadContext , XmlDictionaryString , XmlDictionaryString , CollectionDataContract )\r\n   at System.Runtime.Serialization.CollectionDataContract.ReadXmlValue(XmlReaderDelegator xmlReader, XmlObjectSerializerReadContext context)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract& dataContract)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Int32 id, RuntimeTypeHandle declaredTypeHandle, String name, String ns)\r\n   at ReadEntityCollectionFromXml(XmlReaderDelegator , XmlObjectSerializerReadContext , XmlDictionaryString[] , XmlDictionaryString[] )\r\n   at System.Runtime.Serialization.ClassDataContract.ReadXmlValue(XmlReaderDelegator xmlReader, XmlObjectSerializerReadContext context)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract& dataContract)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Int32 id, RuntimeTypeHandle declaredTypeHandle, String name, String ns)\r\n   at ReadKeyValuePairOfstringanyTypeFromXml(XmlReaderDelegator , XmlObjectSerializerReadContext , XmlDictionaryString[] , XmlDictionaryString[] )\r\n   at System.Runtime.Serialization.ClassDataContract.ReadXmlValue(XmlReaderDelegator xmlReader, XmlObjectSerializerReadContext context)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract& dataContract)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Int32 id, RuntimeTypeHandle declaredTypeHandle, String name, String ns)\r\n   at ReadParameterCollectionFromXml(XmlReaderDelegator , XmlObjectSerializerReadContext , XmlDictionaryString , XmlDictionaryString , CollectionDataContract )\r\n   at System.Runtime.Serialization.CollectionDataContract.ReadXmlValue(XmlReaderDelegator xmlReader, XmlObjectSerializerReadContext context)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator reader, String name, String ns, Type declaredType, DataContract& dataContract)\r\n   at System.Runtime.Serialization.XmlObjectSerializerReadContext.InternalDeserialize(XmlReaderDelegator xmlReader, Type declaredType, DataContract dataContract, String name, String ns)\r\n   at System.Runtime.Serialization.DataContractSerializer.InternalReadObject(XmlReaderDelegator xmlReader, Boolean verifyObjectName, DataContractResolver dataContractResolver)\r\n   at System.Runtime.Serialization.XmlObjectSerializer.ReadObjectHandleExceptions(XmlReaderDelegator reader, Boolean verifyObjectName, DataContractResolver dataContractResolver)\r\n   at System.Runtime.Serialization.XmlObjectSerializer.ReadObject(XmlDictionaryReader reader)\r\n   at Microsoft.Crm.Sandbox.SandboxUtility.DeserializeDataContract[T](Byte[] serializedDataContract, Assembly proxyTypesAssembly)\r\n   at Microsoft.Crm.Sandbox.SandboxExecutionContext.Merge(IExecutionContext originalContext)\r\n   at Microsoft.Crm.Sandbox.SandboxCodeUnit.ExecuteInternal(SandboxClient client, IExecutionContext context, SandboxTraceContext sandboxTraceContext, SandboxCallTracker callTracker, Guid parentExecutionId, String assemblyContents, Boolean& isSafeToRetry, Boolean& executeDone)\r\n   at Microsoft.Crm.Sandbox.SandboxCodeUnit.<>c__DisplayClass24_0.<Execute>b__0(): Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #BBF0AE79",
            "type": "System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=9.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]",
            "stacktrace": "   at Microsoft.Crm.Extensibility.OrganizationSdkServiceInternal.Execute(OrganizationRequest request, CorrelationToken correlationToken, CallerOriginToken callerOriginToken, WebServiceType serviceType, Boolean checkAdminMode, ExecutionContext executionContext, Dictionary`2 optionalParameters)\r\n   at Microsoft.Crm.Extensibility.OData.CrmODataExecutionContext.Execute(OrganizationRequest request, ExecutionContext executionContext)\r\n   at Microsoft.Crm.Extensibility.OData.CrmODataServiceDataProvider.ExecuteOperation(CrmODataExecutionContext context, EdmOperation edmOperation, Dictionary`2 parameters, Dictionary`2 boundParameters)\r\n   at Microsoft.Crm.Extensibility.OData.ActionController.ProcessOperationRequest(String operationName, Dictionary`2 operationParameters, EntityReference entityReference, String boundEntityName, String boundEntityType)\r\n   at Microsoft.Crm.Extensibility.OData.ActionController.<>c__DisplayClass9_0.<PostUnboundAction>b__0()\r\n   at Microsoft.PowerApps.CoreFramework.ActivityLoggerExtensions.Execute[TResult](ILogger logger, EventId eventId, ActivityType activityType, Func`1 func, IEnumerable`1 additionalCustomProperties)\r\n   at Microsoft.Xrm.Telemetry.XrmTelemetryExtensions.Execute[TResult](ILogger logger, XrmTelemetryActivityType activityType, Func`1 func)\r\n   at lambda_method(Closure , Object , Object[] )\r\n   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>c__DisplayClass10.<GetExecutor>b__9(Object instance, Object[] methodParameters)\r\n   at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ExecuteAsync(HttpControllerContext controllerContext, IDictionary`2 arguments, CancellationToken cancellationToken)\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Web.Http.Controllers.ApiControllerActionInvoker.<InvokeActionAsyncCore>d__0.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Web.Http.Controllers.ActionFilterResult.<ExecuteAsync>d__2.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Web.Http.Dispatcher.HttpControllerDispatcher.<SendAsync>d__1.MoveNext()"
        }
    }
}

Why I got that error, or maybe I can't return EntityCollection on my Output Parameter ? because when I return string it works fine.

EDIT

Here is my Code Below

using Microsoft.Xrm.Sdk;
using Microsoft.Xrm.Sdk.Query;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Runtime.Serialization;
using System.Xml;

namespace Plugins.GlobalActions
{
    public class ACTGetData : IPlugin
    {

        public void Execute(IServiceProvider serviceProvider)
        {
            const string PROCESSUNIQUENAME = "MJT_ACTGETDATA";

            IPluginExecutionContext context = (IPluginExecutionContext)serviceProvider.GetService(typeof(IPluginExecutionContext));
            IOrganizationServiceFactory serviceFactory = (IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
            IOrganizationService service = serviceFactory.CreateOrganizationService(context.UserId);
            if(context.MessageName.ToUpper() == PROCESSUNIQUENAME)
            {
                if(context.InputParameters["BookableResource"] == null)
                {
                    throw new InvalidPluginExecutionException("Bookable Resource Can't be null");
                }
                Guid bookableResource = new Guid(Convert.ToString(context.InputParameters["BookableResource"]));



                QueryExpression queryBookingStatus = new QueryExpression("bookingstatus");
                queryBookingStatus.Criteria.AddCondition(new ConditionExpression("name", ConditionOperator.Equal, "Scheduled"));
                var bookingStatus = service.RetrieveMultiple(queryBookingStatus);
                if (bookingStatus != null)
                {
                    QueryExpression queryBookableResourceboking = new QueryExpression("bookableresourcebooking");
                    queryBookableResourceboking.ColumnSet = new ColumnSet(true);
                    queryBookableResourceboking.Criteria.AddCondition("resource", ConditionOperator.Equal, bookableResource);
                    EntityCollection bookableResourceBookingEntity = service.RetrieveMultiple(queryBookableResourceboking);

                    if (bookableResourceBookingEntity.Entities.Count > 0)
                    {

                        context.OutputParameters["BookableResourceBooking"] = new EntityCollection(new List<Entity> { bookableResourceBookingEntity.Entities.FirstOrDefault(), bookableResourceBookingEntity.Entities[0] });
                    }
                }



            }

        }
    }
}

My Postman Request

organization.crm5.dynamics.com/.../MyActionName

{

 "BookableResource" : "{BookableResourceGuid}"

}

Suppose I have an Output Parameter with name 'Result2'. Following is the code to send output parameter to custom action-

 context.OutputParameters["Result2"] = new EntityCollection(new List<Entity> { entitlements.FirstOrDefault(), order}); //entitlements is List<Entity> object, order is Entity object

For the action,please make sure Stage of Execution is Post Operation.

Updated the post-

For EntityCollection we do not need to specify a target entity as shown in image below.

This allows us to send an entity collection with objects of separate entities. As you can see from image below, I have sent entitlement and salesorder entity objects in a single list.

Script to call action is below. I have used Process.JS for calling the action. Here is the URL for process.js. Kindly add it to the form on which you have to call the action.GitHub link

function CreateRenewals() {
    Xrm.Page.ui.setFormNotification("Please wait, this may take some time..", "INFORMATION", "1");
    Process.callAction("gc_CreateRenewalOpportunity",
            [{
                key: "TargetOrder",
                type: Process.Type.EntityReference,
                value: new Process.EntityReference("salesorder", Xrm.Page.data.entity.getId())
            }],
            function (params) {
                debugger;//Success
                Xrm.Page.ui.clearFormNotification("1");
                Xrm.Page.ui.setFormNotification(params.Result, "INFORMATION", "2");
            },
            function (e, t) {
                Xrm.Page.ui.clearFormNotification("1");
                Xrm.Page.ui.setFormNotification(params.Result, "INFORMATION", "3");
                // Error
            });
}

    public void Execute(IServiceProvider serviceProvider)
        {
            ITracingService tracer = (ITracingService)serviceProvider.GetService(typeof(ITracingService));
            IPluginExecutionContext context = (IPluginExecutionContext)serviceProvider.GetService(typeof(IPluginExecutionContext));
            IOrganizationServiceFactory factory = (IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
            IOrganizationService service = factory.CreateOrganizationService(context.UserId);

            try
            {
                Entity entity = null;
                if (context.InputParameters.Contains("TargetOrder"))
                {
                    if (context.InputParameters["TargetOrder"] is Entity)
                        entity = (Entity)context.InputParameters["TargetOrder"];
                    else if (context.InputParameters["TargetOrder"] is EntityReference)
                    {
                        EntityReference entityRef = (EntityReference)context.InputParameters["TargetOrder"];
                        entity = service.Retrieve(entityRef.LogicalName, entityRef.Id, new Microsoft.Xrm.Sdk.Query.ColumnSet(true));
                    }
                }
                context.OutputParameters["Result2"] = new EntityCollection(new List<Entity> { entity });
}

Hope it helps.