Activity Party

 using Microsoft.Xrm.Sdk;

using Microsoft.Xrm.Sdk.Query;

using System;

using System.Collections.Generic;

public class RetrieveActivityParty

{

    private readonly IOrganizationService _service;

    public RetrieveActivityParty(IOrganizationService service)

    {

        _service = service;

    }

    public void GetActivityParties(Guid activityId)

    {

        QueryExpression query = new QueryExpression("activityparty")

        {

            ColumnSet = new ColumnSet("partyid", "participationtypemask")

        };

        query.Criteria.AddCondition("activityid", ConditionOperator.Equal, activityId);

        EntityCollection results = _service.RetrieveMultiple(query);

        foreach (Entity activityParty in results.Entities)

        {

            EntityReference party = activityParty.GetAttributeValue<EntityReference>("partyid");

            int participationType = activityParty.GetAttributeValue<OptionSetValue>("participationtypemask")?.Value ?? 0;

            Console.WriteLine($"Party ID: {party?.Id}, Type: {party?.LogicalName}, Participation Type: {participationType}");

        }

    }

}

---------

string fetchXml = $@"

    <fetch>

        <entity name='activityparty'>

            <attribute name='partyid' />

            <attribute name='participationtypemask' />

            <filter>

                <condition attribute='activityid' operator='eq' value='{activityId}' />

            </filter>

        </entity>

    </fetch>";

EntityCollection results = _service.RetrieveMultiple(new FetchExpression(fetchXml));

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