How to get the CRM Entity Name from the Object Type Code of a RegardingID?

Question

So it seems that it is a fairly common question in CRM to try get the object type code when you have an entity name. But since I always have to do things the hard way, I have the reverse task: I have the object type code, and need to get the entity name.

In general, the ultimate task is to take the the CRM regarding information on an email, and use it to query CRM for additional info. I can get the regardingID and the object type code easily. And for standard entities I can use a hardcoded lookup to get an entity name. But for custom entities, this won't work, as the object type code can be different in different organizations.

To get the regardingID and object type code:

string regardingId;
regardingId = (String)(item.PropertyAccessor.GetProperty("http://schemas.microsoft.com/mapi/string/{00020329-0000-0000-C000-000000000046}/crmRegardingId"));

dynamic crmRegardingObjectType;
crmRegardingObjectType = item.PropertyAccessor.GetProperty("http://schemas.microsoft.com/mapi/string/{00020329-0000-0000-C000-000000000046}/crmRegardingObjectType");

I could do a request to retrieve metadata for all entities & find the appropriate object type code, but this is really slow and way too much data:

RetrieveAllEntitiesRequest entitiesRequest = new RetrieveAllEntitiesRequest();
entitiesRequest.EntityFilters = EntityFilters.Entity;
RetrieveAllEntitiesResponse response = (RetrieveAllEntitiesResponse)service.Execute(entitiesRequest);

I have to think there is a better way, but I have been stuck for a while.

ANSWER This is what I ended up doing:

        string entityLogicalName = String.Empty;

        MetadataFilterExpression EntityFilter = new MetadataFilterExpression(LogicalOperator.And);
        EntityFilter.Conditions.Add(new MetadataConditionExpression("ObjectTypeCode", MetadataConditionOperator.Equals, objectTypeCode));

        MetadataPropertiesExpression mpe = new MetadataPropertiesExpression();
        mpe.AllProperties = false;
        mpe.PropertyNames.Add("DisplayName");
        mpe.PropertyNames.Add("ObjectTypeCode");
        mpe.PropertyNames.Add("PrimaryIdAttribute");
        mpe.PropertyNames.Add("PrimaryNameAttribute");

        EntityQueryExpression entityQueryExpression = new EntityQueryExpression()
        {
            Criteria = EntityFilter,
            Properties = mpe
        };

        RetrieveMetadataChangesResponse initialRequest = GetMetadataChanges(entityQueryExpression, null, DeletedMetadataFilters.OptionSet);
        if (initialRequest.EntityMetadata.Count == 1)
        {
            entityLogicalName = initialRequest.EntityMetadata[0].LogicalName;
        }

        return entityLogicalName;

    protected RetrieveMetadataChangesResponse GetMetadataChanges(EntityQueryExpression entityQueryExpression, String clientVersionStamp, DeletedMetadataFilters deletedMetadataFilter)
    {
        RetrieveMetadataChangesRequest retrieveMetadataChangesRequest = new RetrieveMetadataChangesRequest()
        {
            Query = entityQueryExpression,
            ClientVersionStamp = clientVersionStamp,
            DeletedMetadataFilters = deletedMetadataFilter
        };

        return (RetrieveMetadataChangesResponse)organizationService.Execute(retrieveMetadataChangesRequest);
    }

Answer 1

Since Rollup 12 for CRM 2011 Metadata query is available. So instead of querying of all entities you can try to build query and get only one entity.