VariantChangeTypeEx function (oleauto.h)
This API is affected by the problem described in Microsoft Support topic VarI8FromCy produces incorrect value when CY value is very large.
Converts a variant from one type to another, using an LCID.
HRESULT VariantChangeTypeEx( [out] VARIANTARG *pvargDest, [in] const VARIANTARG *pvarSrc, [in] LCID lcid, [in] USHORT wFlags, [in] VARTYPE vt );
The destination variant. If this is the same as pvarSrc, the variant will be converted in place.
The variant to convert.
The locale identifier. The LCID is useful when the type of the source or destination VARIANTARG is VT_BSTR, VT_DISPATCH, or VT_DATE.
The type to convert to. If the return code is S_OK, the vt field of the *pvargDest is guaranteed to be equal to this value.
This function can return one of these values.
||The variant type is not a valid type of variant.|
||The data pointed to by pvarSrc does not fit in the destination type.|
||The argument could not be coerced to the specified type.|
||One of the arguments is not valid.|
||Insufficient memory to complete the operation.|
The VariantChangeTypeEx function handles coercions between the fundamental types (including numeric-to-string and string-to-numeric coercions). A variant that has VT_BYREF set is coerced to a value by obtaining the referenced value. An object is coerced to a value by invoking the object's Value property (DISPID_VALUE).
Typically, the implementer of IDispatch::Invoke determines which member is being accessed, and then calls VariantChangeType to get the value of one or more arguments. For example, if the IDispatch call specifies a SetTitle member that takes one string argument, the implementer would call VariantChangeTypeEx to attempt to coerce the argument to VT_BSTR.
If VariantChangeTypeEx does not return an error, the argument could then be obtained directly from the bstrVal field of the VARIANTARG. If VariantChangeTypeEx returns DISP_E_TYPEMISMATCH, the implementer would set *puArgErr to 0 (indicating the argument in error) and return DISP_E_TYPEMISMATCH from IDispatch::Invoke.
Arrays of one type cannot be converted to arrays of another type with this function.