syntax to use near 'xxx= @@IDENTITY' (no replies)

Why output param @Id is replaced by Null ?
My Code:
try
{
string connetStr = "data source=127.0.0.1;database=Test; uid=root;pwd=root;Allow User Variables=True;";
MySqlConnection conn = new MySqlConnection(connetStr);
conn.Open();
string sql =
@"INSERT T_Test_Table
(
Name
)
VALUES
(
@Name -- Name - nvarchar(50)
);
SET @Id = @@IDENTITY";
MySqlCommand cmd = new MySqlCommand(sql, conn);
MySqlParameter mpName = new MySqlParameter("Name", MySqlDbType.VarChar, 50);
mpName.Value = "Tests";
mpName.Direction = ParameterDirection.Input;
MySqlParameter mpId = new MySqlParameter("@Id", MySqlDbType.Int32);
mpId.Direction = ParameterDirection.Output;
cmd.Parameters.Add(mpName);
cmd.Parameters.Add(mpId);
int iRes = cmd.ExecuteNonQuery();
cmd.Parameters.Clear();
conn.Close();
}
catch (Exception ex)
{
Console.WriteLine(ex.ToString());
throw new Exception("Mysql ExecuteNonQuery Error:\r\n" + ex.Message, ex);
}