RoParseTypeName function

Parses a type name and existing type parameters, in the case of parameterized types.


HRESULT RoParseTypeName(
  HSTRING typeName,
  DWORD   *partsCount,
  HSTRING **typeNameParts




String-encoded typename. The typename can be a non-namespace-qualified type, a non-parameterized namespace-qualified type or a fully instantiated namespace-qualified parameterized type.


Type: DWORD*

Number of elements in the typenameParts array.



The first element of the array is the specified type, and the remaining array elements are the type parameters (if any) in prewalk tree order.

Return Value


This function can return one of these values.

Return code Description
Parsing was successful.
typeName contains embedded nulls or is empty.
typename is not well formed.


The RoParseTypeName function parses the string-encoded type name and returns an array of HSTRING values. The first element of the array is the base type, and the remaining array elements are the type parameters, if any, in pre-order tree traversal order. S_OK is returned if the parsing was successful.

Here are examples of different possible input typenames:

  • Example 1 (non-namespace-qualified type)
    • Input typename


    • Output

      Array element 0: String

  • Example 2 (non-parameterized namespace-qualified type)
    • Input typename


    • Output

      Array element 0: Windows.Foundation.IExtensionInformation

  • Example 3 (instantiated parameterized interface type)
    • Input typename

      Windows.Foundation.Collections.IIterator1&lt;Windows.Foundation.Collections.IMapView2<Windows.Foundation.Collections.IVector`1<String>, String>>

    • Output

      Array element 0: Windows.Foundation.Collections.IIterator`1

      Array element 1: Windows.Foundation.Collections.IMapView`2

      Array element 2: Windows.Foundation.Collections.IVector`1

      Array element 3: String

      Array element 4: String

When parsing a non-parameterized type, the RoParseTypeName function returns an array that has one element. Please refer to example 1 and example 2 above.

The input string must be non-empty and it must not contain any embedded null characters. Otherwise, the API fails with E_INVALIDARG. If the typename is ill-formed, like IVector`1<, then the API will fail with the RO_E_METADATA_INVALID_TYPE_FORMAT error code.

The RoParseTypeName function validates only the format of the typename and not its syntax. For example, the function validates that a namespace-qualified parameterized interface typename follows the format shown in the following table, but it does not impose any requirements on what characters/symbols can be used in the typename, except that it should not contain ` , <, or > characters.

The format for a string-encoded instantiated parameterized interface is as follows:

Name of parameterized interface Backtick character (`) Number of type parameters Left angle bracket (<) Namespace qualified name of each type parameter, separated by commas. Right angle bracket (>)

Type parameters may be:

  • Non-parameterized, non-namespace-qualified types, like WinRT fundamental types.
  • Non-parameterized namespace-qualified types.
  • Fully-instantiated namespace-qualified parameterized interfaces.
On success, the caller is responsible for deallocating the typenameParts array returned by RoParseTypeName by using CoTaskMemFree to free the array and WindowsDeleteString to free the HSTRING values.


The following C++ example shows how to use the RoParseTypeName function to find the direct child namespaces for a specified type name.

#include <windows.h>
#include <stdio.h>
#include <WinRTString.h>
#include <TypeResolution.h>

HRESULT PrintParameterizedInterfaceParts(PCWSTR pszTypename);

int ShowUsage() { wprintf(L"Usage: RoParseTypeNameSample "TypeName"\n"); return -1; }

int __cdecl wmain(int argc, WCHAR **argv) { if (argc != 2) { return ShowUsage(); }

HRESULT hr = PrintParameterizedInterfaceParts(argv[1]);

if (SUCCEEDED(hr))
    return 0;
    return -1;


HRESULT PrintParameterizedInterfaceParts(PCWSTR pszTypename) { HRESULT hr; HSTRING hstrTypeName = nullptr; HSTRING *phstrNameParts = nullptr; DWORD cRetrievedNameParts = 0;

hr = WindowsCreateString(

if (SUCCEEDED(hr))
    hr = RoParseTypeName(

if (SUCCEEDED(hr))
    wprintf(L"Parameterized interface %s is composed of:\n", pszTypename);

    for (UINT32 i = 0; i &lt; cRetrievedNameParts; i++)
        wprintf(L"Element %d: %s\n", i, WindowsGetStringRawBuffer(phstrNameParts[i], nullptr));
    wprintf(L"Invalid parameterized interface syntax: %s!\n", pszTypename);

// Clean up resources.
if (hstrTypeName != nullptr)

for (UINT32 i = 0; i &lt; cRetrievedNameParts; i++)


return hr;



Minimum supported client Windows 8 [desktop apps | UWP apps]
Minimum supported server Windows Server 2012 [desktop apps | UWP apps]
Target Platform Windows
Header rometadataresolution.h
Library WinTypes.lib
DLL WinTypes.dll