Converts a variant from one type to another, using a LCID.
The return value obtained from the returned HRESULT is one of the following.
The variant type vt 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 invalid.
Memory could not be allocated for the conversion.
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 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 field 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.
The type of a VARIANTARG should not be changed in the rgvarg array in place.