枚举值从0开始，因此

typedef enum _AUDCLNT_SHAREMODE
{ 
    AUDCLNT_SHAREMODE_SHARED, 
    AUDCLNT_SHAREMODE_EXCLUSIVE 
} AUDCLNT_SHAREMODE;

实际上等同于

typedef enum _AUDCLNT_SHAREMODE
{ 
    AUDCLNT_SHAREMODE_SHARED = 0, 
    AUDCLNT_SHAREMODE_EXCLUSIVE = 1 
} AUDCLNT_SHAREMODE;