Query schema definitions and detect changes

This sample shows how to retrieve and detect changes in table definitions using RetrieveMetadataChangeRequest method. You can view the sample at PowerApps-Samples/dataverse/orgsvc/C#-NETCore/Schema/RetrieveMetadataChanges/

See these topics for explaination of functionality:

• Query schema definitions
• Cache Schema data

How to run this sample

See the instructions here: Schema samples instructions

Demonstrates

This sample shows how to retrieve schema definitions for a specific set of column definitions and save them (in memory) to represent a cache.

Then it creates a new column, retrieves the data for only that new column, which it adds to the cache.

Then it deletes the column, retrieves data about deleted items and uses it to remove the deleted column definition from the cache.

This sample has 6 sections:

Define query

Define a query using EntityQueryExpression that will return all the Picklist choice columns from the contact table.

Initialize cache

1. Create an instance of RetrieveMetadataChangesRequest with the Query parameter set to the query.
2. Send the request using IOrganizationService.Execute.
3. Cache the RetrieveMetadataChangesResponse.EntityMetadata value.
4. Save the RetrieveMetadataChangesResponse.ServerVersionStamp value for use in the next request.
5. Write a list of all the current columns in the cache.

Add choice column

Create a new choice column by creating a new PicklistAttributeMetadata instance in the contact table attributes.

Detect added column

1. Create a new instance of RetrieveMetadataChangesRequest with the Query parameter set to the original query.
2. Set the RetrieveMetadataChangesRequest.ClientVersionStamp with the value previously returned from the first request.
3. Send the request using IOrganizationService.Execute.
4. Verify that only one new column definition was returned to represent the choice column that was created.
5. Save the RetrieveMetadataChangesResponse.ServerVersionStamp value for use in the next request.
6. Add that choice column data to the cache.

Delete choice column

Delete the choice column created earlier.

Detect deleted column

1. Create a new instance of RetrieveMetadataChangesRequest with the Query parameter set to the original query.
2. Set the RetrieveMetadataChangesRequest.ClientVersionStamp with the value previously returned from the second request.
3. Set the RetrieveMetadataChangesRequest.DeletedMetadataFilters to DeletedMetadataFilters.Attribute because we are only looking for deleted column definitions.
4. Send the request using IOrganizationService.Execute.
5. Find the Id of the deleted choice column in the RetrieveMetadataChangesResponse.DeletedMetadata, using DeletedMetadataFilters.Attribute as an index value for the collection.
6. Remove the column definition from the cache.
7. Write a list of all the current columns in the cache.

Clean up

No clean up is required because all data created by this sample was deleted.