C# FileStream設置了FileAccess.ReadWrite, FileShare.ReadWrite依然報“流不可讀”或者“流不可寫”

今天遇見一個詭異的事情，我用FileStream操作一個文件的時候，明明設置了FileAccess.ReadWrite, FileShare.ReadWrite了，但是依然報錯，說是“流不可寫”

后來仔細一研究才發現，原來是我用的不對，我是在FileStream里面先用了BinaryReader，然后又用了BinaryWriter，貌似不能這么用，一個FileStream只能用做一次操作

 

static void AAA() {
            using (FileStream fs = new FileStream("E:\\test.txt", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite)) {
                using (BinaryReader br = new BinaryReader(fs)) {
                    Console.WriteLine(br.ReadByte());
                    br.Dispose();
                } 
                using (BinaryWriter bw = new BinaryWriter(fs)) {  //一個FileStream只能進行一次Binary操作，第二次就會報錯

                }
            }
        }

　　不知道為什么using包裹着BinaryReader也不行，我還想着重用一個流呢，估計是沒徹底釋放之類的，想要不報錯，就需要給BinaryWriter再申請一次FileStream

static void AAA() {
            using (FileStream fs = new FileStream("E:\\test.txt", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite)) {
                using (BinaryReader br = new BinaryReader(fs)) {
                    Console.WriteLine(br.ReadByte());
                    br.Dispose();
                }

            }
            using (FileStream fs = new FileStream("E:\\test.txt", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite)) {
                using (BinaryWriter bw = new BinaryWriter(fs)) {  //每個Binary操作都申請一次FileStream就不會報錯了

                }
            }
        }

　　或者干脆直接用FileStream自己操作算了

static void AAA() {
            using (FileStream fs = new FileStream("E:\\test.txt", FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite)) {
                Console.WriteLine(fs.ReadByte());
                fs.Seek(0,SeekOrigin.Begin);
                fs.WriteByte(0xFF);
            } 
        }