Platform SDK: Interprocess Communications

DdeCreateStringHandle

The DdeCreateStringHandle function creates a handle that identifies the specified string. A dynamic data exchange (DDE) client or server application can pass the string handle as a parameter to other Dynamic Data Exchange Management Library (DDEML) functions.

HSZ DdeCreateStringHandle(
  DWORD idInst,  // instance identifier
  LPTSTR psz,    // pointer to null-terminated string
  int iCodePage  // code page identifier
);

Parameters

idInst: [in] Specifies the application instance identifier obtained by a previous call to the DdeInitialize function.
psz: [in] Pointer to a buffer that contains the null-terminated string for which a handle is to be created. This string can be up to 255 characters. The reason for this limit is that DDEML string management functions are implemented using global atoms.
iCodePage: [in] Specifies the code page used to render the string. This value should be either CP_WINANSI (the default code page) or CP_WINUNICODE, depending on whether the ANSI or Unicode version of DdeInitialize was called by the client application.

Return Values

If the function succeeds, the return value is a string handle.

If the function fails, the return value is 0L.

Errors

The DdeGetLastError function can be used to get the error code, which can be one of the following values:

DMLERR_INVALIDPARAMETER
DMLERR_NO_ERROR
DMLERR_SYS_ERROR

Remarks

The value of a string handle is not related to the case of the string it identifies.

When an application either creates a string handle or receives one in the callback function and then uses the DdeKeepStringHandle function to keep it, the application must free that string handle when it is no longer needed.

An instance-specific string handle cannot be mapped from string handle to string and back to string handle. This is shown in the following example, in which the DdeQueryString function creates a string from a string handle and DdeCreateStringHandle creates a string handle from that string, but the two handles are not the same:

DWORD idInst; 
DWORD cb; 
HSZ hszInst, hszNew; 
PSZ pszInst; 
 
DdeQueryString(idInst, hszInst, pszInst, cb, CP_WINANSI); 
hszNew = DdeCreateStringHandle(idInst, pszInst, CP_WINANSI); 
// hszNew != hszInst !

Requirements