使用流阅读器读取文本文件时出错

Question

1) 我正在尝试读取一个文本文件，但它显示错误喜欢

foreach 语句不能对“System.IO.StreamReader”类型的变量进行操作，因为“System.IO.StreamReader”不能 包含“GetEnumerator”的公共定义

这是我的 C# 代码...

 using (StreamReader sr = new StreamReader(@"D:\test1.txt"))
            {
                while (sr.Peek() >= 0)
                {
                    //contents of foreach loop go here

                        foreach (var line in sr)
                        {
                            var items = line.Split(new[] { '\t', '\n' }).ToArray();
                            if (items.Length != 3)
                                continue;
                            var Name = items[0].ToString();
                            var Email = items[1].ToString();
                            var Pwd = items[2].ToString();
                            cmd.CommandText = "insert into Employees values('" + Name + "','" + Email + "','" + Pwd + "')";
                            cmd.CommandType = CommandType.Text;
                            cmd.ExecuteNonQuery();
                        }

                }

Answer 1

基本上，Alex.K 的评论是怎么说的：

using (StreamReader sr = new StreamReader(@"D:\test1.txt"))
{
    while (sr.Peek() >= 0)
    {
        var line = sr.ReadLine();
        var items = line.Split(new[] { '\t', '\n' }).ToArray();
        if (items.Length != 3)
            continue;
        var Name = items[0].ToString();
        var Email = items[1].ToString();
        var Pwd = items[2].ToString();
        cmd.CommandText = "insert into Employees values('" + Name + "','" + Email + "','" + Pwd + "')";
        cmd.CommandType = CommandType.Text;
        cmd.ExecuteNonQuery();
    }
}

您不需要在 peek 检查循环中使用foreach，只需读取一行即可。

这里有一个来自MSDN的典型用法，很清楚怎么读行：

        using (StreamReader sr = new StreamReader(path)) 
        {
            while (sr.Peek() >= 0) 
            {
                Console.WriteLine(sr.ReadLine());
            }
        }

编辑

为了避免著名的SQL injection vulnerability，使用Parameters处理参数：

// this is baaaaad
cmd.CommandText = "insert into Employees values('" + Name + "','" + Email + "','" + Pwd + "')";

// will become
cmd.CommandText = "insert into Employees values(@Name, @Email, @Pwd)";
cmd.Parameters["@Name"].Value = Name;
cmd.Parameters["@Email"].Value = Email;
cmd.Parameters["@Pwd"].Value = Pwd;

// somewhere before, where you create command
cmd.Parameters.Add("@Name", type);
cmd.Parameters.Add("@Email", type);
cmd.Parameters.Add("@Pwd", type);

Answer 2

错误很明显。

您只能通过foreach 对实现GetEnumerator 方法的元素进行迭代，而StreamReader 不是。

StreamReader 有很多优秀的和好的例子，随便看看。

Answer 3

这将为此工作。使用while 循环代替ForEach 循环

using (StreamReader sr = new StreamReader(@"D:\test1.txt"))
 {
      while (sr.Peek() >= 0)
      {
       //contents of foreach loop go here

       while ((line = sr.ReadLine()) != null)
       {
       var items = line.Split(new[] { '\t', '\n' }).ToArray();
       if (items.Length != 3)
                    continue;
       var Name = items[0].ToString();
       var Email = items[1].ToString();
       var Pwd = items[2].ToString();
       cmd.CommandText = "insert into Employees values('" + Name + "','" + Email + "','" + Pwd + "')";
       cmd.CommandType = CommandType.Text;
       cmd.ExecuteNonQuery();


          }
  }

Answer 4

你可以在这种类型中使用

foreach (var line in File.ReadLines(@"D:\test1.txt"))
{
}