等待文件被进程释放

问题描述

如何等待文件空闲，以便 ss.Save() 可以用新文件覆盖它?如果我同时运行两次(ish)，我会收到 generic GDI+ 错误.

How do I wait for the file to be free so that ss.Save() can overwrite it with a new one? If I run this twice close together(ish), I get a generic GDI+ error.

///<summary>
/// Grabs a screen shot of the App and saves it to the C drive in jpg
///</summary>
private static String GetDesktopImage(DevExpress.XtraEditors.XtraForm whichForm)
{
    Rectangle bounds = whichForm.Bounds;

    // This solves my problem but creates a clutter issue
    // var timeStamp = DateTime.Now.ToString("ddd-MMM-dd-yyyy-hh-mm-ss");
    // var fileName = "C:\HelpMe" + timeStamp + ".jpg";

    var fileName = "C:\HelpMe.jpg";
    File.Create(fileName);
    using (Bitmap ss = new Bitmap(bounds.Width, bounds.Height))
    using (Graphics g = Graphics.FromImage(ss))
    {
        g.CopyFromScreen(whichForm.Location, Point.Empty, bounds.Size);
        ss.Save(fileName, ImageFormat.Jpeg);
    }

    return fileName;
}

推荐答案

像这样的函数可以做到:

A function like this will do it:

public static bool IsFileReady(string filename)
{
    // If the file can be opened for exclusive access it means that the file
    // is no longer locked by another process.
    try
    {
        using (FileStream inputStream = File.Open(filename, FileMode.Open, FileAccess.Read, FileShare.None))
            return inputStream.Length > 0;
    }
    catch (Exception)
    {
        return false;
    }
}

把它放在一个 while 循环中，你有一些东西会阻塞直到文件可访问:

Stick it in a while loop and you have something which will block until the file is accessible:

public static void WaitForFile(string filename)
{
    //This will lock the execution until the file is ready
    //TODO: Add some logic to make it async and cancelable
    while (!IsFileReady(filename)) { }
}

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