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so I have a form with a ComboBox that I populate with a list of open processes (In this case, I limit it to processes with titles that have 13 characters.) When I select an Item in the ComboBox I want to find that Form by Title and BringToFront However when I do so, it throws a System.NullReferenceException.

Here's the code I use to populate the box.

using HWND = IntPtr;
public static class OpenWindowGetter
{
    /// <summary>Returns a dictionary that contains the handle and title of all the open windows.</summary>
    /// <returns>A dictionary that contains the handle and title of all the open windows.</returns>
    public static IDictionary<HWND, string> GetOpenWindows()
    {
        HWND shellWindow = GetShellWindow();
        Dictionary<HWND, string> windows = new Dictionary<HWND, string>();

        EnumWindows(delegate (HWND hWnd, int lParam)
        {
            if (hWnd == shellWindow) return true;
            if (!IsWindowVisible(hWnd)) return true;

            int length = GetWindowTextLength(hWnd);
            if (length == 0) return true;

            StringBuilder builder = new StringBuilder(length);
            GetWindowText(hWnd, builder, length + 1);

            windows[hWnd] = builder.ToString();
            return true;

        }, 0);

        return windows;
    }

    private delegate bool EnumWindowsProc(HWND hWnd, int lParam);

    [DllImport("USER32.DLL")]
    private static extern bool EnumWindows(EnumWindowsProc enumFunc, int lParam);

    [DllImport("USER32.DLL")]
    private static extern int GetWindowText(HWND hWnd, StringBuilder lpString, int nMaxCount);

    [DllImport("USER32.DLL")]
    private static extern int GetWindowTextLength(HWND hWnd);

    [DllImport("USER32.DLL")]
    private static extern bool IsWindowVisible(HWND hWnd);

    [DllImport("USER32.DLL")]
    private static extern IntPtr GetShellWindow();
}

public void populateIncidents()
    {
        foreach (KeyValuePair<IntPtr, string> window in OpenWindowGetter.GetOpenWindows())
        {
            IntPtr handle = window.Key;
            string title = window.Value;
            if (title.Length == 13)
            {
                chooseIncidentBox.Items.Add(title);
            }
        }
    }

And here's the code I'm using to try to show the Form.

private void chooseIncidentBox_SelectedIndexChanged(object sender, EventArgs e)
    {
        sSelectedIncident = chooseIncidentBox.Text;
        Application.OpenForms[sSelectedIncident].BringToFront(); //Exception thrown here.
    }

I'm not quite sure why it's throwing the exception, I know the Form exists as it wouldn't populate the ComboBox otherwise. Any help would be greatly appreciated.

4

1 回答 1

2

您拥有的代码提供了所有活动窗口。现在，Application.OpenForms仅适用于在您的应用程序中打开的表单。例如，如果您的应用程序中有ParentFormand并且两者都是打开的，则集合将包含这两个。ChildFormOpenForms

您正在寻找的是把任何进程窗口放在前面。你可以利用SetForegroundWindowinUser32.dll来做到这一点。这个SO question 看起来与您需要的非常相似。看看接受的解决方案。

于 2015-10-20T04:29:03.203 回答