How do you check for permissions to write to a directory or file?

UPDATE:

Modified the code based on this answer to get rid of obsolete methods.

You can use the Security namespace to check this:

public void ExportToFile(string filename)
{
    var permissionSet = new PermissionSet(PermissionState.None);    
    var writePermission = new FileIOPermission(FileIOPermissionAccess.Write, filename);
    permissionSet.AddPermission(writePermission);

    if (permissionSet.IsSubsetOf(AppDomain.CurrentDomain.PermissionSet))
    {
        using (FileStream fstream = new FileStream(filename, FileMode.Create))
        using (TextWriter writer = new StreamWriter(fstream))
        {
            // try catch block for write permissions 
            writer.WriteLine("sometext");


        }
    }
    else
    {
        //perform some recovery action here
    }

}

As far as getting those permission, you are going to have to ask the user to do that for you somehow. If you could programatically do this, then we would all be in trouble 😉

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