IPropertySystem::FormatForDisplayAlloc method

Gets a string representation of a property value to an allocated memory buffer.


HRESULT FormatForDisplayAlloc(
  [in]  REFPROPERTYKEY        key,
  [in]  REFPROPVARIANT        propvar,
  [out] LPWSTR                *ppszDisplay


key [in]


A reference to the desired PROPERTYKEY.

propvar [in]


A reference to a PROPVARIANT structure that contains the type and value of the property.

pdff [in]


The format of the property string. See PROPDESC_FORMAT_FLAGS.

ppszDisplay [out]


When this method returns, contains a pointer to the formatted value as a null-terminated, Unicode string.

Return value


Returns one of the following values.

Return codeDescription

Formatted string is created. This string may be returned empty due to an empty input string or from a non-empty value that was formatted as an empty string.


Formatted string is not created. Indicates that the empty string resulted from a VT_EMPTY.


Indicates allocation failed.



You must initialize Component Object Model (COM) with CoInitialize or OleInitialize before calling IPropertySystem::FormatForDisplayAlloc.

On success, this method gets a formatted Unicode string representation of a property value for a specified PROPERTYKEY, and one or more PROPDESC_FORMAT_FLAGS. If the PROPERTYKEY is not recognized by the schema subsystem, IPropertySystem::FormatForDisplayAlloc attempts to format the value according to its VARTYPE.

This method allocates memory for the buffer and returns a pointer to it at ppszDisplay. The calling application must use CoTaskMemFree to release the string specified by ppszDisplay when it is no longer needed.

The purpose of this method is to convert data into a string suitable for display to the user. The value is formatted according to the current locale, the language of the user, the PROPDESC_FORMAT_FLAGS, and the property description specified by the property key. For information about how the property description schema influences the formatting of the value, see displayInfo, stringFormat, booleanFormat, numberFormat, NMDATETIMEFORMAT, and enumeratedList. Typically, the PROPDESC_FORMAT_FLAGS are used to modify the format prescribed by the property description.

The output string may contain Unicode directional characters. These nonspacing characters influence the Unicode bidirectional algorithm so that the values appear correctly when a left to right (LTR) language is drawn on a right to left (RTL) window, and vice versa. These characters include the following: "\x200e", "\x200f", "\x202a", "\x202b", "\x202c", "\x202d", "\x202e".

The following properties use special formats and are unaffected by the PROPDESC_FORMAT_FLAGS (examples cited are for strings with a current locale set to English; typically, output is localized except where noted).

System.FileAttributesThe following file attributes are converted to letters and appended to create a string (for example, a value of 0x1801 (FILE_ATTRIBUTE_READONLY | FILE_ATTRIBUTE_COMPRESSED | FILE_ATTRIBUTE_OFFLINE) is converted to "RCO"):
  • FILE_ATTRIBUTE_READONLY (0x00000001) - 'R'
  • FILE_ATTRIBUTE_SYSTEM (0x00000004) - 'S'
  • FILE_ATTRIBUTE_ARCHIVE (0x00000020) -'A'
  • FILE_ATTRIBUTE_COMPRESSED (0x00000800) - 'C'
  • FILE_ATTRIBUTE_ENCRYPTED (0x00004000) - 'E'
  • FILE_ATTRIBUTE_OFFLINE (0x00001000) - 'O'
System.Photo.ISOSpeedFor example, "ISO-400".

The APEX value is converted to an exposure time using this formula:

Exposure_time = 2^(-APEX_value)

For example, "2 sec."or "1/125 sec.".

System.Photo.ExposureTimeFor example, "2 sec."or "1/125 sec."

The APEX value is converted to an F number using this formula:

F_Number = 2^(APEX_Value / 2)

For example, "f/5.6".

System.Photo.FNumberFor example, "f/5.6".
System.Photo.SubjectDistanceFor example, "15 m"or "250 mm".
System.Photo.FocalLengthFor example, "50 mm".
System.Photo.FlashEnergyFor example, "500 bpcs".
System.Photo.ExposureBiasFor example, "-2 step", " 0 step", or "+3 step".
System.Computer.DecoratedFreeSpaceFor example, "105 MB free of 13.2 GB".
System.ItemTypeFor example, "Application" or "JPEG Image".
System.ControlPanel.CategoryFor example, "Appearance and Personalization".
System.ComputerNameFor example, "LITWARE05 (this computer)" or "testbox07".


If the property key does not correspond to a property description in any of the registered property schemas, then this method chooses a format based on the type of the value.

Type of the valueFormat
VT_BOOLEANNot supported.
VT_FILETIMEDate/time string as specified by PROPDESC_FORMAT_FLAGS and the current locale. PDFF_SHORTTIME and PDFF_SHORTDATE are the default. For example, "11/13/2006 3:22 PM".
Numeric VARTYPEDecimal string in the current locale. For example, "42".
VT_LPWSTR or otherConverted to a string. Sequences of "\r", "\t", or "\n" are replaced with a single space.
VT_VECTOR | anythingSemicolon separated values—a semicolon is used regardless of locale.



Minimum supported client

Windows Vista [desktop apps only]

Minimum supported server

Windows Server 2008 [desktop apps only]


Windows Desktop Search (WDS) 3.0





See also

Property Description Schema



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