Here are the classes, structs, unions and interfaces with brief descriptions:

[detail level 12]

►Nxml
CXmlDelegate	Interface for overriding XML handling (must be capable of handling multiple threads)
CXmlDocument
CXmlLoadException
CXmlNamespace
CXmlNode
CXmlParserException
CXmlReader	XmlReader abstraction class
CAccessDeniedError	The user could not get access to the content. For example, no permissions, content revoked
CAction	Interface for an action. Each action translates to a step that needs to be taken by the application to apply the label (as defined in the policy)
CActionData
CAddContentFooterAction	An action class that specifies adding a content footer to the document
CAddContentHeaderAction	An action class that specifies adding content header
CAddDynamicWatermarkAction	An action class that specifies adding watermark
CAddDynamicWatermarkActionData
CAddWatermarkAction	An action class that specifies adding watermark
CAddWatermarkActionData
CAdhocProtectionRequiredError	Adhoc protection should be set to complete the action on the file
CApplicationActionState
CApplicationInfo	A struct that includes application specific information
CApplyLabelAction	Apply label actions requires the calling application to apply a specific label
CArgumentData
CAsyncControl	Class used to cancel async operation
CAuditDelegate	A class that defines the interface to the MIP SDK audit notifications
CAuditEvent	A single audit event
►CAuthDelegate	Delegate for auth related operations
COAuth2Challenge	Class that contains all the information required from the calling application in order to generate an oauth2 token
COAuth2Token	A class containing access token info provided by an application
CBadInputError	Bad input error, thrown when the input to an SDK API is invalid
CClassificationData
CClassificationRequest	Class that contains the request of a classification call on the Execution State
CClassificationResult	Class that contains the result of a classification call on the Execution State
►CComputeEngine
CSettings
CComputeEngineContext
CConditionData
CConsentDelegate	Delegate for consent related operations
CConsentDeniedError	An operation that required consent from user was not granted consent
CContentFormatNotSupportedError	Content Format is not supported
CContentLabel	Abstraction for a Microsoft Information Protection label that is applied to a piece of content, typically a document
CContentMarkingActionData
CCustomAction	CustomAction is a generic action class that captures all the sub-properties of the action as a property bag. The caller is responsible to understand the meaning of the action
CCustomerKeyUnavailableError	Bring your own encryption key needed and unavailable
CDelegateResponseError	Delegate Response Error. Thrown or returned in response to encountering an error in a delegate method
CDelegationLicense
CDelegationLicenseSettings
CDeprecatedApiError	Caller invoked a deprecated API
CDetailedClassificationResult	Class that contains the result of a classification call on the Execution State
CDiagnosticConfiguration	Custom diagnostic configurations (not commonly used)
CDiagnosticDelegate	A class that defines the interface to the MIP SDK audit/telemetry notifications
CDirectoryObject	The directory object information which includes- type, email, objectId and PUID
CDirectoryObjectRights	The directory object and rights associated with it
CDocumentState
CDynamicWatermark	Representation of the dynamic watermark which the admin has configured for a label
CEditableStream
CError	Base class for all errors that will be reported (thrown or returned) from MIP SDK
CEvent	A single audit/telemetry event
CEventContext	A single audit/telemetry event context
CEventProperty	A single audit/telemetry property
CExecutionState	Interface for all the state needed to execute the engine
CExtendedErrorInfo
CFileExecutionState
►CFileHandler	Interface for all file handling functions
CObserver	Observer interface for clients to get notifications events related to file handler
CFileInspector
CFileIOError	File IO error
►CFileProfile	FileProfile class is the root class for using the Microsoft Information Protection operations
CObserver	Observer interface for clients to get notifications for profile related events
CSettings	Settings used by FileProfile during its creation and throughout its lifetime
CFileStatus	Interface for all file status functions
CGetTemplatesSettings	Settings to use when obtaining templates
CHttpDelegate	Interface for overriding HTTP handling
CHttpOperation	Interface that describes a single HTTP operation, implemented by client app when overriding HttpDelegate
CHttpRequest	Interface that describes a single HTTP request
CHttpResponse	Interface that describes a single HTTP response, implemented by client app when overriding HttpDelegate
CIdentity	Abstraction for identity
CInsufficientBufferError	Insufficient buffer error
CInternalError	Internal error. This error is thrown when something unexpected happens during execution
CJsonDelegate
CJsonDocument	JsonDocument abstraction class
CJsonValue
CJustificationRequiredError
CJustifyAction	Justify Action requires providing a justification to a label downgrade and setting the response in the execution state
CLabel	Abstraction for a single Microsoft Information Protection label
CLabelActionData
CLabelDisabledError	Label is disabled or inactive
CLabelGroupData
CLabelInfo	Label information for a template or ad-hoc (custom) protection
CLabelingOptions	Interface for configuring labeling options for the SetLabel/DeleteLabel methods
CLabelNotFoundError	Label ID is not recognized
CLicenseApplicationData	The application data from a license
CLicenseConnectionInfo	The connection information from a license
CLicenseDescriptor	The descriptor from a license
CLicenseInfo	Representation of the dynamic watermark which the admin has configured for a label
CLicenseNameAndDescriptionItem	The descriptor line item from a license
CLicenseNotRegisteredError	License is not registered
CLicenseRightsData	The rights related information of the publishing license
CLoggerConfiguration	Configuration to use when default logging is enabled. This is set only once per process and any later change will be ignored
CLoggerDelegate	A class that defines the interface to the MIP SDK logger
CLogMessageData	A class that stores log messages
CMetadataAction	An Action that adds metadata information to the content
CMetadataEntry	An abstraction class for metadata entry
CMetadataVersion	Interface for a MetadataVersion. MetadataVersion determines which metadata is active and how it is processed
CMipConfiguration	Configuration used by MIP sdk during its creation and throughout its lifetime
CMipContext	MipContext represents state that is shared across all profiles, engines, handlers
CMsgAttachmentData
CMsgInspector
CNetworkError	Networking error. Caused by unexpected behavior when making network calls to service endpoints
CNoAuthTokenError	The user could not get access to the content due to missing authentication token
CNoPermissionsError	The user could not get access to the content. For example, no permissions, content revoked
CNoPermissionsExtendedError	The user could not get access to the content due to extended Access checks like ABAC
CNoPolicyError	Tenant policy is not configured for classification/labels
CNotSupportedError	The operation requested by the application is not supported by the SDK
COperationCancelledError	Operation was cancelled
CParsedPublishingLicense
CParsedPublishingLicenseBuilder
CPolicyHandler	This class provides an interface for all policy handler functions on a file
CPolicyPackageData
CPolicyRuleData
CPrivilegedRequiredError	Current label was assigned as a privileged operation (The equivalent to an administrator operation), therefore it can't be overriden
CPropertyData
CProtectAdhocAction	An action class that specifies adding adhoc protection to the document
CProtectAdhocDkAction	An action class that specifies adding adhoc double key protection to the document
CProtectByEncryptOnlyAction	An action class that specifies adding encrypt only protection to the document
CProtectByTemplateAction	An action class that specifies adding protection by template to the document
CProtectDoNotForwardAction	An action class that specifies adding do not forward protection to the document
CProtectDoNotForwardDkAction	An action class that specifies adding do not forward double key protection to the document
CProtectionActionData
CProtectionCommonSettings	Settings to use for protection operations
CProtectionDescriptor	Description of protection associated with a piece of content
CProtectionDescriptorBuilder	Constructs a ProtectionDescriptor that describes protection associated with a piece of content
►CProtectionEngine	Manages protection-related actions related to a specific identity
CObserver	Interface that receives notifications related to ProtectionEngine
CSettings	Settings used by ProtectionEngine during its creation and throughout its lifetime
►CProtectionHandler	Manages protection-related actions for a specific protection configuration
CConsumptionSettings	Settings used to create a ProtectionHandler to consume existing content
CObserver	Interface that receives notifications related to ProtectionHandler
CPublishingSettings	Settings used to create a ProtectionHandler to protect new content
►CProtectionProfile	ProtectionProfile is the root class for performing protection operations
CObserver	Interface that receives notifications related to ProtectionProfile
CSettings	Settings used by ProtectionProfile during its creation and throughout its lifetime
CProtectionSettings	Interface for configuring protection options for the SetLabel method
CProxyAuthenticationError	Proxy authentication failure
CPublishingLicenseInfo	Holds the details of a Publishing License used to create a protection handler
CPublishingUseLicenseRequest	Request for a use license in the publishing request
CRecommendLabelAction	Recommend label actions is meant to suggest a label to the users. Suppressing this call after a user ignores the recommended label should be done through the supported actions on the execution state
CRemoveContentFooterAction	An action class that specifies removing the content footer from the document
CRemoveContentHeaderAction	An action class that specifies removing the content header from the document
CRemoveDynamicWatermarkAction	An action class that specifies removing the watermarking from the document
CRemoveProtectionAction	An action class that specifies removing protection from the document
CRemoveWatermarkAction	An action class that specifies removing the watermarking from the document
CRulePackageData
CSensitiveTypeClassificationData
CSensitivityConditionData
CSensitivityTypesRulePackage
CServiceDisabledError	The user could not get access to the content due to a service being disabled
►CStorageDelegate	A class that defines the interface to the MIP SDK storage for caching
CStorageSettings	Settings used by StorageDelegate
CStorageTable	A class that defines the interface to the MIP SDK storage table used for caching
CStream	A class that defines the interface between the MIP SDK and stream-based content
CSyncFileBaseData
CSyncFilePolicyData
CSyncFileSensitivityData
CTaskDispatcherDelegate	A class that defines the interface to the MIP SDK task dispatcher
CTelemetryDelegate	A class that defines the interface to the MIP SDK telemetry notifications
CTelemetryEvent	A single telemetry event
CTemplateArchivedError	Template ID is archived and unavailable for protection
CTemplateDescriptor
CTemplateNotFoundError	Template ID is not recognized by RMS service
CTenantInformation	Tenant information from RMS
CUniqueIdsAndContentFormats
CUserRights	A group of users and the rights associated with them
CUserRoles	A group of users and the roles associated with them