static void Main(string[] args)
{
// 删除已存在文件
if (File.Exists(testFile))
{
File.Delete(testFile);
}
// 写入一些东西以便后面读取
using (FileStream stream = File.Create(testFile))
{
string content = "我是文件具体内容，我是不是帅得掉渣？";
byte[] contentByte = Encoding.UTF8.GetBytes(content);
stream.Write(contentByte, 0, contentByte.Length);
}
// 开始异步读取文件具体内容
using (FileStream stream = new FileStream(testFile, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize, FileOptions.Asynchronous))
{
byte[] data = new byte[bufferSize];
// 将自定义类型对象实例作为参数
ReadFileClass rfc = new ReadFileClass(stream, data);
// 开始异步读取
IAsyncResult result = stream.BeginRead(data, 0, data.Length, FinshCallBack, rfc);
// 模拟做了一些其他的操作
Thread.Sleep(3 * 1000);
Console.WriteLine("主线程执行完毕，按回车键退出程序");
}
Console.ReadKey();
}
/// <summary>
/// 异步读文件
/// </summary>
/// <param name="path">文件路径</param>
/// <param name="callBack">回调返回读取的数据</param>
/// <param name="bufferSize">缓冲区大小</param>
public static void ReadFileAsync(string path, Action <byte[]> callBack, int bufferSize = 1024)
{
action = callBack;
using (Stream stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize, FileOptions.Asynchronous))
{
byte[] data = new byte[bufferSize];
ReadFileClass rfc = new ReadFileClass(stream, data);
IAsyncResult result = stream.BeginRead(data, 0, data.Length, FinshCallBack, rfc);
}
}
/// <summary>
/// 完成异步操作后的回调方法
/// </summary>
/// <param name="result">状态对象</param>
private static void FinshCallBack(IAsyncResult result)
{
ReadFileClass rfc = result.AsyncState as ReadFileClass;
if (rfc != null)
{
// 必须的步骤：让异步读取占用的资源被释放掉
int length = rfc.stream.EndRead(result);
// 获取读取到的文件内容
byte[] fileData = new byte[length];
Array.Copy(rfc.data, 0, fileData, 0, fileData.Length);
string content = Encoding.UTF8.GetString(fileData);
// 打印读取到的文件基本信息
Console.WriteLine("读取文件结束：文件长度为[{0}]，文件内容为[{1}]", length.ToString(), content);
}
}
private static void FinshCallBack(IAsyncResult result)
{
if (result == null)
{
return;
}
ReadFileClass rfc = result.AsyncState as ReadFileClass;
int length = rfc.stream.EndRead(result);
byte[] fileData = new byte[length];
Array.Copy(rfc.data, 0, fileData, 0, fileData.Length);
if (action != null)
{
action(fileData);
}
}
