solucionado gracias... estoy trabajando con framework 2.0 asi que no sirve datediff, cree un metodo
Código:
private int GetMonths(DateTime dtt1, DateTime dtt2)
{
bool isBigger = dtt1 >= dtt2;
DateTime dttBegin = !isBigger ? dtt1 : dtt2;
DateTime dttEnd = isBigger ? dtt1 : dtt2;
int count = 0;
while (dttBegin < dttEnd)
{
dttBegin = dttBegin.AddMonths(1);
count++;
}
return isBigger ?
((count) * -1) : (count - 1);
}