文件流、流读取器和流写入器的问题

Question

我的第一个问题的形式是，如果我以这种方式声明我的文件流等，

filestream file;
streamreader file_in;
streamwriter file_out;

try
{
    file = new filestream("data.txt", FileMode.OpenOrCreate);
    file_in = new streamreader(file);
    file_out = new streamwriter(file);
}
catch(IOException exc)
{
    Console.WriteLine(exc.Message);
}

则会抛出一个错误，提示“使用未分配的局部变量”，我觉得这很奇怪，因为所有流都是在 try 块之外但在 main 中声明的，因此它们应该存在于 main 中。

我的另一个问题的形式是，如果我删除 try/catch 块并将流声明为一行（例如： FileStream file = new FileStream("data.txt", FileMode.OpenOrCreate, FileAccess.ReadWrite) ;）我从文件中的读取确实有效，但是我无法写入文件。我的写入文件功能如下：

    public bool write_to_file(ref StreamWriter file_out)
    {
        if (this.is_empty == true)
        {
            Console.WriteLine("error, there is nothing to write.");
            Console.WriteLine("press any key to continue...");
            Console.ReadKey();
            return false;
        }

        try
        {
            string temp = this.is_empty + "," + this.movie_title + "," + this.year_released + "," + this.publisher + "," +
                this.length + "," + this.acting_rating + "," + this.music_rating + "," + this.cinematography_rating + "," +
                this.plot_rating + "," + this.duration_rating + "," + this.total_rating;
            file_out.WriteLine(temp);
            return true;
        }
        catch (IOException exc)
        {
            Console.WriteLine(exc.Message);
            Console.WriteLine("press any key to continue...");
            Console.ReadKey();
            return false;
        }
    }

任何帮助将不胜感激，谢谢。

Answer 1

好吧，它们已声明但未分配...因此，要么将它们设置为 null，要么一起执行所有操作。

try
{
    using(var file = new FileStream("data.txt", FileMode.OpenOrCreate))
    using(var file_in = new StreamReader(file))
    using(var file_out = new StreamWriter(file))
    {
        // Do your thing
    }
}
catch
{
    throw;
}

Answer 2

您需要为顶部的变量分配一个值，即使它只是 null

FileStream   file     = null;
StreamReader file_in  = null;
StreamWriter file_out = null;

Answer 3

在关闭文件之前，请尝试刷新输出流和文件。

 file_out.Flush();
 file.Flush(); // may be redundant but won't hurt