IDL Interfaces Reference

Visual Studio’s extensibility APIs are defined in Interface Definition Language (IDL) files. This reference covers the key interface families.

IDL File Categories

Category	Files	Purpose
Core Shell	vsshell*.idl	Main VS Shell interfaces
Text/Editors	textmgr*.idl	Text buffer/view management
Debugging	msdbg*.idl	Debug engine interfaces
Symbol Providers	sh.idl, ee.idl	Symbol handlers, expression evaluators
Source Control	IVsSccManager*.idl	SCC integration

IVs* Interface Family

Hierarchy & Projects

Interface	Purpose
IVsHierarchy	Base hierarchy interface for projects and items
IVsProject	Project management
IVsProjectFactory	Project creation
IVsHierarchyEvents	Hierarchy change notifications

Windows & UI

Interface	Purpose
IVsWindowFrame	Tool/document window frame
IVsWindowFrameNotify	Window notifications
IVsUIShell	UI shell services
IVsUIHierWinClipboardHelper	Clipboard operations

Text/Editor

Interface	Purpose
IVsTextBuffer	Text storage
IVsTextView	Text display/editing
IVsCodeWindow	Code editor window
IVsColorizer	Syntax highlighting
IVsLanguageInfo	Language service info

Selection

Interface	Purpose
IVsMonitorSelection	Selection tracking
IVsMultiItemSelect	Multi-selection support

Persistence

Interface	Purpose
IVsPersistSolutionOpts	Solution options persistence
IVsPersistSolutionProps	Solution properties persistence
IVsSolutionPersistence	Solution save/load

IDebug* Interface Family

Core

Interface	Purpose
IDebugCoreServer2/3	Debug server
IDebugSession2/3	Debug session
IDebugEventCallback2	Debug event notifications

Engine

Interface	Purpose
IDebugEngine2/3	Debug engine

Process/Program

Interface	Purpose
IDebugProcess2	Process management
IDebugProgram2	Program debugging
IDebugProgramNode2	Program tree node

Execution

Interface	Purpose
IDebugThread2/3	Thread debugging
IDebugStackFrame2	Stack frame inspection
IDebugCodeContext2	Code location

Breakpoints

Interface	Purpose
IDebugBoundBreakpoint2	Active breakpoint
IDebugPendingBreakpoint2	Pending breakpoint
IDebugErrorBreakpoint2	Failed breakpoint

VSITEMID Architecture

Special Item IDs

VSITEMID_NIL        = ((DWORD)-1)  // No nodes
VSITEMID_ROOT       = ((DWORD)-2)  // Hierarchy root
VSITEMID_SELECTION  = ((DWORD)-3)  // Selected items

Nodes are identified by VSITEMID + IVsHierarchy interface pairs. Nodes are NOT COM objects themselves - they use opaque cookies.

Language GUIDs

guidCLang          // C language
guidCPPLang        // C++ language
guidVBLang         // VB.NET language
guidCSharpLang     // C# language (implicit)
guidFSharpLang     // F# language
guidSQLLang        // SQL language
guidJScriptLang    // JScript language
guidVBScriptLang   // VBScript language

Debug Engine GUIDs

guidNativeOnlyEng           // Native-only engine
guidCOMPlusOnlyEng          // Managed-only engine
guidCOMPlusNativeEng        // Mixed-mode engine
guidScriptEng               // Script engine
guidSQLEng                  // SQL engine
guidCoreSystemClrEng        // Core CLR engine

Property Filters (IDebugProperty2)

guidFilterLocals              // Local variables
guidFilterAllLocals           // All locals
guidFilterArgs                // Function arguments
guidFilterLocalsPlusArgs      // Locals and arguments
guidFilterRegisters           // CPU registers
guidFilterThis                // 'this' pointer

Error Codes

Edit & Continue

Code	Name
0x80044001	E_ENC_REBUILD_FAIL
0x80044002	E_ENC_COMMIT_FAIL
0x80044003	E_ENC_APPLY_FAIL
0x80044004	E_ENC_INTERNAL_ERROR

Text Buffer

Code	Name
0x80044001	BUFFER_E_READONLY
0x80044002	BUFFER_E_READONLY_REGION
0x80044003	BUFFER_E_TIMEOUT
0x80044004	BUFFER_E_LOCKED
0x80044005	BUFFER_E_SCC_READONLY

Text View

Code	Name
0x80044201	VIEW_E_NO_BOOKMARKS
0x80044202	VIEW_E_NO_DEBUGGER
0x80044204	VIEW_E_USERREADONLY
0x80044205	VIEW_E_LOCATION_HIDDEN

Version Numbering

IDL files use version numbers mapping to VS releases:

Version	Visual Studio
80	VS 2005
90	VS 2008
100	VS 2010
110	VS 2012
120	VS 2013
140	VS 2015
150	VS 2017
160	VS 2019
170	VS 2022