P/Invoke Odbccp32

Odbccp32.cs

    public class Odbccp32
    {
        /// <summary>
        /// From sql.h
        /// </summary>
        private const int SQL_MAX_MESSAGE_LENGTH = 512;

        [DllImport(nameof(Odbccp32), CharSet = CharSet.Unicode, SetLastError = true)]
        [return: MarshalAs(UnmanagedType.Bool)]
        public static extern bool SQLGetInstalledDrivers(char[] lpszBuf, ushort cbufMax, out ushort pcbBufOut);

        [DllImport(nameof(Odbccp32))]
        public static extern SqlReturnCode SQLInstallerError(int iError, out SqlInstallerErrorCode pfErrorCode, StringBuilder lpszErrorMsg, int cbErrorMsgMax, out int pcbErrorMsg);

        public static string[] GetOdbcDriverNames()
        {
            string[] odbcDriverNames = null;
            char[] driverNamesBuffer = new char[ushort.MaxValue];
            ushort size;

            bool succeeded = SQLGetInstalledDrivers(driverNamesBuffer, ushort.MaxValue, out size);

            if (!succeeded)
            {
                string message = GetErrorMessage();
                throw new ApplicationException($"Error within a PIvoke call. {message}");
            }

            char[] driverNames = new char[size - 1];
            Array.Copy(driverNamesBuffer, driverNames, size - 1);
            odbcDriverNames = (new string(driverNames)).Split('\0');

            return odbcDriverNames;
        }

        public static bool IsSqlServer2016DriverInstalled()
        {
            return true; //GetOdbcDriverNames().Any(d => d.Equals("ODBC Driver 13 for SQL Server", StringComparison.OrdinalIgnoreCase));
        }

        private static string GetErrorMessage()
        {
            StringBuilder result = new StringBuilder();

            SqlInstallerErrorCode pfErrorCode;
            int bufferSizeNeeded;
            int errorRecord = 1;

            SqlReturnCode returnCode = SQLInstallerError(errorRecord, out pfErrorCode, result, SQL_MAX_MESSAGE_LENGTH, out bufferSizeNeeded);

            if (returnCode == SqlReturnCode.SQL_SUCCESS_WITH_INFO)
            {
                while (bufferSizeNeeded >= SQL_MAX_MESSAGE_LENGTH)
                {
                    StringBuilder partialMessage = new StringBuilder();

                    returnCode = SQLInstallerError(++errorRecord, out pfErrorCode, partialMessage, SQL_MAX_MESSAGE_LENGTH, out bufferSizeNeeded);

                    if (returnCode != SqlReturnCode.SQL_NO_DATA)
                    {
                        result.Append(partialMessage);
                    }
                }
            }

            if (returnCode == SqlReturnCode.SQL_ERROR)
            {
                result.Append("SQLInstallerError cannot access error values");
            }

            return result.ToString();
        }

    }

    /// <summary>
    /// From sql.h
    /// </summary>
    public enum SqlReturnCode
    {
        SQL_ERROR = -1,
        SQL_SUCCESS = 0,
        SQL_SUCCESS_WITH_INFO = 1,
        SQL_NO_DATA = 100
    }

    /// <summary>
    /// From odbcinst.h
    /// </summary>
    public enum SqlInstallerErrorCode
    {
        ODBC_ERROR_GENERAL_ERR = 1,
        ODBC_ERROR_INVALID_BUFF_LEN = 2,
        ODBC_ERROR_COMPONENT_NOT_FOUND = 6,
        ODBC_ERROR_OUT_OF_MEM = 21
    }