CHString::Format(UINT,...) method (chstring.h)

[The CHString class is part of the WMI Provider Framework which is now considered in final state, and no further development, enhancements, or updates will be available for non-security related issues affecting these libraries. The MI APIs should be used for all new development.]

The Format method formats and stores a series of characters and values in a CHString string.


void  throw(CHeap_Exception) Format(
  UINT nFormatID,



String resource identifier that contains the format control string.


Argument list.

Return value



Each optional argument (if any) is converted and output according to the corresponding format specification in lpszFormat, or from the string resource identified by nFormatID.

Note To reduce exposure to security attacks, always use a format string for Format. For example, Format(input) is exploitable, and Format("%s", input) is not. Never use a user-supplied string for the format string. If your format string is stored for a purpose such as localization, ensure that the string is protected from unauthorized write access. If your function writes to a string rather than standard output, you may need to avoid using a trailing "%s" in the format string.

If the string object is offered as a parameter to Format, the call fails. For example, the following code causes unpredictable results.


CHString str = L"Some Data";

// Attention: str is also used in the parameter list.
str.Format(L"%s%d", str, 123);

Note  When you pass a character string as an optional argument, you must cast it explicitly as LPCWSTR. The format argument has the same form and function as the format argument for the printf function. A NULL character is appended to the end of the written characters.


Requirement Value
Header chstring.h

See also