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This interface provides methods for accessing a library of type descriptions.

The data that describes a set of objects is stored in a type library. A type library can be a stand-alone binary file (.tlb), a resource in a dynamic link library or executable file (.dll or .exe), or part of a compound document file.

The system registry contains a list of all the installed type libraries.

This interface supports the following:

  • Generalized containment for type information. ITypeLib allows iteration over the type descriptions contained in the library.
  • Global functions and data. A type library can contain descriptions of a set of modules, each of which is the equivalent of a C or C++ source file that exports data and functions. The type library supports compiling references to the exported data and functions.
  • General information, including a user-readable name for the library and help for the library as a whole.

The following table shows the methods for this interface in alphabetical order. Like all COM interfaces, this interface inherits the methods for the IUnknown interface.

Method Description


This method finds occurrences of a type description in a type library. This may be used to verify that a name exists in a type library.


This method retrieves the library's documentation string, the complete Help file name and path, and the context identifier for the library Help topic.


This method retrieves the structure that contains the library's attributes.


This method retrieves a pointer to the ITypeComp for a type library. This enables a client compiler to bind to the library's types, variables, constants, and global functions.


This method retrieves the specified type description in the library.


This method retrieves the number of type descriptions in the library.


This method retrieves the type description that corresponds to the specified globally unique identifier (GUID).


This method retrieves the type of a type description.


This method indicates whether a passed-in string contains the name of a type or a member described in the library.


This method releases the TLIBATTR originally obtained from GetLibAttr.

Headeroaidl.h, oaidl.idl
Libraryoleaut32.lib, uuid.lib
Windows Embedded CEWindows CE 2.0 and later
Windows MobileWindows Mobile Version 5.0 and later