//文件沖突測試
FileStream fs1 = new FileStream("readtest1.txt", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
int i1 = fs1.ReadByte();
FileStream fs2 = new FileStream("readtest1.txt",FileMode.Open,FileAccess.Read,FileShare.ReadWrite);

textBox1.Text = i1.ToString()+"\r\n";

FileStream fs3 = new FileStream("
 
readtest1.txt", FileMode.Create,FileAccess.Write);
fs3.WriteByte(24);
fs3.Flush();
int i2 = fs2.ReadByte();
textBox1.Text += i2.ToString();
fs3.Close();
fs2.Close();
fs1.Close();

FileAccess.Read指定文件為Read，FileShare.ReadWrite指定其他進程可以讀寫該文件。如不加FileShare.ReadWrite只加FileAccess.Read則只能同時讀，不加FileAccess.Read則同時讀也不行。

C# 文件同時讀寫