怎样创建文件
我想在C#中实现以下功能：当文件不存在时，创建；当文件存在时，改写。
我下面的代码编译没有问题，但是不能创建和改写文件。请指点
string filePath = "test.txt";
//Response.Write(filePath);
StreamWriter sw = new StreamWriter(filePath, false, Encoding.Unicode);
string content = "aaaaaaaaaaaaaaaa";
sw.Write(content);
sw.Flush();
sw.Close();

[解决办法]

C# code

if (File.Exists(Server.MapPath("Test.txt")))        {            FileStream fs = new FileStream(Server.MapPath("Test.txt"),FileMode.OpenOrCreate,FileAccess.Write);            StreamWriter sw = new StreamWriter(fs);            sw.WriteLine("测试");            sw.Close();            fs.Close();        }        else        {            File.Create(Server.MapPath("Test.txt"));            FileStream fs = new FileStream(Server.MapPath("Test.txt"), FileMode.Open, FileAccess.Write);            StreamWriter sw = new StreamWriter(fs);            sw.WriteLine("测试");            sw.Close();            fs.Close();        }