c# - 使用未分配的局部变量 - SQL + C#

Question

我试图让服务器从 SQL 数据库读取 int 'rank'，但是我收到“使用未分配的局部变量”，因为它不会读取 'rank'，直到它应该被设置一个 while 语句，但是我无法将其移出，因为它在进入 try 和 catch 之前不会执行 SQL 查询。

具体在这里:

using (var rdr = cmd.ExecuteReader())
            {
                while (rdr.Read())
                rank = rdr.GetInt32("rank");
            }

完整代码:

class Ban : ICommand
{
    public string Command { get { return "ban"; } }
    public int RequiredRank { get { return 3; } }

    public void Execute(Player player, string[] args)
    {
        int rank;
        string name = "'" + args[0] + "'";
        if (args.Length == 0)
        {
            player.SendHelp("Usage: /ban <username>");
        }
        try
        {
            using (Database dbx = new Database())
            {
                var cmd = dbx.CreateQuery();
                cmd.CommandText = "SELECT rank FROM accounts where name=@name";
                cmd.Parameters.AddWithValue("@name", name);
                cmd.ExecuteNonQuery();
                using (var rdr = cmd.ExecuteReader())
                {
                    while (rdr.Read())
                    rank = rdr.GetInt32("rank");
                }
                Console.Write("{0} ({1}) tried to ban {2}({3})", player.Name, player.Client.Account.Rank, name, rank);
                 if (rank < player.Client.Account.Rank)
                {
                    var cmda = dbx.CreateQuery();
                    cmda.CommandText = "UPDATE accounts SET banned=1, rank=0 WHERE name=@name";
                    cmda.Parameters.AddWithValue("@name", args[0]);
                    if (cmda.ExecuteNonQuery() == 0)
                    {
                        player.SendInfo("Could not ban");
                    }
                    else
                    {
                        foreach (var i in player.Owner.Players)
                        {
                            if (i.Value.nName.ToLower() == args[0].ToLower().Trim())
                            {
                                i.Value.Client.Disconnect();
                                player.SendInfo("Account successfully Banned");
                                Console.ForegroundColor = ConsoleColor.Yellow;
                                Console.Out.WriteLine(args[0] + " was Banned.");
                                Console.ForegroundColor = ConsoleColor.White;
                            }
                        }
                    }
                }
                 else if (rank >= player.Client.Account.Rank)
                    player.SendInfo("Could not ban");
            }
        }
        catch
        {
            player.SendInfo("Could not ban");
        }
    }
}

Answer 1

编译器警告您，该变量在您使用时可能尚未分配。

using (var rdr = cmd.ExecuteReader())
{
   while (rdr.Read())
   rank = rdr.GetInt32("rank");
}

rdr.Read() 可能会立即返回 false，并且不会发生排名分配。

在声明的地方初始化rank，即:intrank = 0;