This function converts a variant from one type to another, using a LCID.
At a Glance
| Header file: | Oleauto.h |
| Windows CE versions: | 2.0 and later |
Syntax
HRESULT VariantChangeTypeEx( VARIANTARG FAR * pvargDest, VARIANTARG FAR * pvarSrc, LCID lcid, unsigned short wFlags, VARTYPE vt);
Parameters
pvargDest
Pointer to the VARIANTARG to receive the coerced type. If this is the same as pvarSrc, the variant is converted in place.
pvarSrc
Pointer to the source VARIANTARG to be coerced.
lcid
LCID for the variant to coerce. The LCID is useful when the type of the source or destination VARIANTARG is VT_BSTR, VT_DISPATCH, or VT_DATE.
wFlags
Flags that control the coercion. The only defined flag is VARIANT_NOVALUEPROP, which prevents the function from attempting to coerce an object to a fundamental type by getting its Value property. Applications should set this flag only if necessary, because it makes their behavior inconsistent with other applications.
vt
Specifies the type to coerce to. If the return code is S_OK, the vt member of the VARIANTARG specified by *pvargDest is guaranteed to be equal to this value.
Return Values
One of the values obtained from the returned HRESULT and described in the following table is returned.
| Value | Description |
| S_OK | Success. |
| DISP_E_BADVARTYPE | The variant type vt is not a valid type of variant. |
| DISP_E_OVERFLOW | The data pointed to by pvarSrc does not fit in the destination type. |
| DISP_E_TYPEMISMATCH | The argument could not be coerced to the specified type. |
| E_INVALIDARG | One of the arguments is invalid. |
| E_OUTOFMEMORY | Memory could not be allocated for the conversion. |
Remarks
Passing into this function any invalid and, under some circumstances, NULL pointers will result in unexpected termination of the application.
The VariantChangeTypeEx function handles coercions between the fundamental types (including numeric-to-string and string-to-numeric coercions). To change a type with the VT_BYREF flag set to one without VT_BYREF, change the referenced value to VariantChangeTypeEx. To coerce objects to fundamental types, obtain the value of the Value property.
Typically, the implementor 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 implementor 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 member of the VARIANTARG. If VariantChangeTypeEx returns DISP_E_TYPEMISMATCH, the implementor 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.
Note
The type of a VARIANTARG should not be changed in the rgvarg array in place.