c# - 文件流、streamreader 和 streamwriter 的问题

Question

我的第一个问题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);
}

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，因为所有流都在 try block 之外但在 main 中声明，因此它们应该存在于 main 中。

我的另一个问题是，如果我删除 try/catch block 并将流声明为一行(例如:FileStream file = new FileStream("data.txt", FileMode.OpenOrCreate, FileAccess .ReadWrite);) 我从文件中读取数据确实有效，但我无法写入文件。我的写文件函数如下:

    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;
        }
    }

非常感谢任何帮助，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;
}