无法获取未共享记录：求C#实现查找未与访问团队共享的Task记录

Let's start by breaking down why your original query isn't giving you the results you want:

• You’re using an Inner Join with principalobjectaccess, which only returns tasks that have been shared with someone (either users or teams). This filters out tasks that haven’t been shared at all.
• Adding principaltypecode != team just excludes team-sharing entries, but still includes tasks shared with users (since those entries have principaltypecode = SystemUser).

To get tasks that are not shared with any teams (including tasks that haven’t been shared with anyone at all), you need to use a NOT EXISTS condition to exclude any task that has a matching entry in principalobjectaccess for a team.

Correct QueryExpression Code #

QueryExpression query = new QueryExpression("task")
{
    ColumnSet = new ColumnSet("activityid", "subject", "customid"),
    Criteria = new FilterExpression
    {
        Conditions = 
        {
            new ConditionExpression("customid", ConditionOperator.NotNull)
        },
        FilterOperator = LogicalOperator.And,
        Filters = 
        {
            new FilterExpression(LogicalOperator.Not)
            {
                Conditions = 
                {
                    // Subquery checks if there's any team sharing entry for the task
                    new ConditionExpression("activityid", ConditionOperator.InSubQuery, 
                        new QueryExpression("principalobjectaccess")
                        {
                            ColumnSet = new ColumnSet("objectid"),
                            Criteria = new FilterExpression
                            {
                                Conditions = 
                                {
                                    new ConditionExpression("objectid", ConditionOperator.Equal, "{activityid}"),
                                    new ConditionExpression("principaltypecode", ConditionOperator.Equal, "team")
                                }
                            }
                        })
                }
            }
        }
    }
};

Alternative Approach with Left Outer Join #

You can also use a left outer join to achieve the same result by filtering out tasks that have no matching team-sharing entries:

QueryExpression query = new QueryExpression("task")
{
    ColumnSet = new ColumnSet("activityid", "subject", "customid"),
    Criteria = new FilterExpression
    {
        Conditions = 
        {
            new ConditionExpression("customid", ConditionOperator.NotNull),
            // Either no shared entries exist, or no team shared entries exist
            new ConditionExpression("POA.objectid", ConditionOperator.Null)
        },
        FilterOperator = LogicalOperator.And
    },
    LinkEntities = 
    {
        new LinkEntity("task", "principalobjectaccess", "activityid", "objectid", JoinOperator.LeftOuter)
        {
            EntityAlias = "POA",
            LinkCriteria = new FilterExpression
            {
                Conditions = 
                {
                    new ConditionExpression("principaltypecode", ConditionOperator.Equal, "team")
                }
            }
        }
    }
};

How XrmToolBox Plugins Typically Implement This #

Most XrmToolBox plugins that find unshared records rely on the NOT EXISTS pattern (the first approach above). Here’s why:

• It directly targets your core requirement: exclude any record that has been shared with teams.
• It’s efficient because it avoids joining large datasets, instead using a subquery to check for the presence of team-sharing entries.
• Some plugins might add extra checks (like filtering out records owned by teams if needed), but the core logic for excluding shared-with-team records is almost always the NOT EXISTS subquery against principalobjectaccess.

Content sourced from Stack Exchange, question author: Nachiket