Access to the path … is denied

问题:

I have created a .msi by using VS2008 setup project. My application frequently writes some value in a .txt file in the application directory (C:\Program Files\MyApp\MyFile.txt). After insalling it in Win7, it raises an exception "Access to the path .... is denied."

But whenever I run it as administrator, no such exception occurs. Here is my sscce

string FilePath=Application.StartupPath + @"\AppSettings\CurrentUserName.inf";
using (StreamWriter writer=new StreamWriter(FilePath,false))
{
    writer.Write(txtLoginName.Text.Trim());
}
MainForm.ProcessLogIn();
this.DialogResult = DialogResult.OK;

I don't know how to solve this problem. Any suggestion?

回答1:

The only way to solve this problem is to not write to that folder. You are not allowed to write to that folder by convention, unfortunately, older versions of Windows did not hold you to this.

Instead, you can use Environment.SpecialFolder to help you find where you need to go:

// your application data for just that User running the app
var perUserAppData = Environment.GetFolderPath(
    Environment.SpecialFolder.ApplicationData);

// your application data for ALL users running the app
var allUsersAppData = Environment.GetFolderPath(
    Environment.SpecialFolder.CommonApplicationData);

// better!
var path = Path.Combine(perUserAppData, @"MyApp\MyFile.txt");

Basically, Windows 7 is telling you that you're going to have to stop driving on the sidewalks and use the street as was intended.

回答2:

Move your file out of Program Files directory. In Win7 is readonly for normal users.

You could move the file in the ProgramData directory.
Your installer should create a directory for your application there.
Then inside your code you could retrieve the correct full pathname using these lines of code

string dataPath = Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData));
string appFile = Path.Combine(dataPath, "MyAppDir", "MyFile.txt");

usually (on Win7) this result in a path like this

c:\programdata\MyAppDir\MyFile.txt

but using the SpecialFolder enum you are guaranteed to use a folder available in readwrite to your application not depending on the current operating system.

回答3:

As a short-term fix, you can use ICACLS to grant write access to the file. Note: NOT the whole directory.

As a longer term fix, you should NOT write to the program directory if you are running as unprivileged users, but instead somewhere like %LOCALAPPDATA% or %APPDATA%.