引用dll
[UnmanagedFunctionPointer(CallingConvention.StdCall)]
public delegate void CallbackDelegate(int error, string info, UserData userData);

    [DllImport("msc.dll", CallingConvention = CallingConvention.StdCall)]
    public static extern IntPtr QISRBuildGrammar(string grammarType, string grammarContent, IntPtr grammarLength, string param, CallbackDelegate callback,  UserData userData);

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class UserData
{

    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 40 /*User_Pass_MAX_SIZE*/)]
    public string grammar_id;

    [MarshalAs(UnmanagedType.SysUInt, SizeConst = 40 /*User_Pass_MAX_SIZE*/)]
    public IntPtr build_fini;

    [MarshalAs(UnmanagedType.SysUInt, SizeConst = 40 /*User_Pass_MAX_SIZE*/)]
    public IntPtr update_fini;


    [MarshalAs(UnmanagedType.SysUInt, SizeConst = 40 /*User_Pass_MAX_SIZE*/)]
    public IntPtr errcode;

}

调用：
UserData udata = new UserData();
string bnf = File.ReadAllText(System.AppDomain.CurrentDomain.BaseDirectory + "call.bnf", Encoding.Default);

            byte[] bytes = Encoding.Default.GetBytes(bnf);
            bytes   = Encoding.Convert(Encoding.Default, Encoding.UTF8,bytes);
            bnf = Encoding.UTF8.GetString(bytes);
            IntPtr len = (IntPtr)bnf.Length;
             IntPtr i = MSCDLL.QISRBuildGrammar("bnf", bnf, len, 
                 "engine_type = local, asr_res_path = fo|res/asr/common.jet, sample_rate = 16000, grm_build_path = res/asr/GrmBuilld", callb, udata);

回调：
private void callb(int error, string info, UserData userData)
{
然后回调里的 error 是23300，语法构建失败。
}