ConfigurationManager可以在Save()上保留XML注释吗？

Question

我写了一个小实用程序,允许我为另一个应用程序的App.config文件更改一个简单的AppSetting,然后保存更改:

 //save a backup copy first.
 var cfg = ConfigurationManager.OpenExeConfiguration(pathToExeFile);
 cfg.SaveAs(cfg.FilePath + "." + DateTime.Now.ToFileTime() + ".bak"); 

 //reopen the original config again and update it.
 cfg = ConfigurationManager.OpenExeConfiguration(pathToExeFile);
 var setting = cfg.AppSettings.Settings[keyName];
 setting.Value = newValue;

 //save the changed configuration.
 cfg.Save(ConfigurationSaveMode.Full); 

这种效果很好,除了一个副作用.新保存的.config文件丢失所有原始XML注释,但仅在AppSettings区域内.是否可以从原始配置文件AppSettings区域保留XML注释？

如果您想快速编译并运行它,那么这是完整源代码的pastebin.

Answer 1

我跳进了Reflector.Net并查看了这个类的反编译源代码.简短的回答是否定的,它不会保留评论.Microsoft编写该类的方法是从配置类的属性生成XML文档.由于注释没有出现在配置类中,因此它们不会将其返回到XML中.

更糟糕的是,Microsoft密封了所有这些类,因此您无法派生新类并插入自己的实现.您唯一的选择是将注释移到AppSettings部分之外,或使用XmlDocument或XDocument类来解析配置文件.

抱歉.这是微软刚刚没有计划的边缘案例.

Answer 2

这是一个可用于保存评论的示例函数。它允许您一次编辑一个键/值对。我还添加了一些内容，以便根据我常用的文件方式很好地格式化文件（如果需要，您可以轻松删除它）。我希望这可以帮助其他人在未来。

public static bool setConfigValue(Configuration config, string key, string val, out string errorMsg) {
    try {
        errorMsg = null;
        string filename = config.FilePath;

        //Load the config file as an XDocument
        XDocument document = XDocument.Load(filename, LoadOptions.PreserveWhitespace);
        if(document.Root == null) {
            errorMsg = "Document was null for XDocument load.";
            return false;
        }
        XElement appSettings = document.Root.Element("appSettings");
        if(appSettings == null) {
            appSettings = new XElement("appSettings");
            document.Root.Add(appSettings);
        }
        XElement appSetting = appSettings.Elements("add").FirstOrDefault(x => x.Attribute("key").Value == key);
        if (appSetting == null) {
            //Create the new appSetting
            appSettings.Add(new XElement("add", new XAttribute("key", key), new XAttribute("value", val)));
        }
        else {
            //Update the current appSetting
            appSetting.Attribute("value").Value = val;
        }


        //Format the appSetting section
        XNode lastElement = null;
        foreach(var elm in appSettings.DescendantNodes()) {
            if(elm.NodeType == System.Xml.XmlNodeType.Text) {
                if(lastElement?.NodeType == System.Xml.XmlNodeType.Element && elm.NextNode?.NodeType == System.Xml.XmlNodeType.Comment) {
                    //Any time the last node was an element and the next is a comment add two new lines.
                    ((XText)elm).Value = "\n\n\t\t";
                }
                else {
                    ((XText)elm).Value = "\n\t\t";
                }
            }
            lastElement = elm;
        }

        //Make sure the end tag for appSettings is on a new line.
        var lastNode = appSettings.DescendantNodes().Last();
        if (lastNode.NodeType == System.Xml.XmlNodeType.Text) {
            ((XText)lastNode).Value = "\n\t";
        }
        else {
            appSettings.Add(new XText("\n\t"));
        }

        //Save the changes to the config file.
        document.Save(filename, SaveOptions.DisableFormatting);
        return true;
    }
    catch (Exception ex) {
        errorMsg = "There was an exception while trying to update the config value for '" + key + "' with value '" + val + "' : " + ex.ToString();
        return false;
    }
}