appsetting详解

1             // Get the application configuration file.
2             System.Configuration.Configuration config =
3               ConfigurationManager.OpenExeConfiguration(
4                     ConfigurationUserLevel.None);
5             string sectionName = "appSettings";
6
7             NameValueCollection appSettings =
8                 ConfigurationManager.AppSettings;
9             List<string> allDatFilesNames;
10
11             allDatFilesNames = GetAllDataFileName();
12             if (allDatFilesNames == null)
13             {
14                 Environment.Exit(0);
15             }
16
17             //先清空之前的数据文件记录
18             config.AppSettings.Settings.Clear();
19             // Save the configuration file.
20             config.Save(ConfigurationSaveMode.Modified);
21
22             // Force a reload of the changed section. This
23             // makes the new values available for reading.
24             ConfigurationManager.RefreshSection(sectionName);
25             appSettings =
26                 ConfigurationManager.AppSettings;
27
28             foreach (string fullName in allDatFilesNames)
29             {
30                 string fileName = Path.GetFileName(fullName);
31                 if (appSettings[fileName] == null)
32                 {
33                     // 键值仅保存文件名 www.zzzyk.com
34                     config.AppSettings.Settings.Add(fileName, GetFileItemNum(fullName).ToString());
35                 }
36                 else
37                 {
38                     // 已存在此键值，则仅刷新
39                     config.AppSettings.Settings[fileName].Value = GetFileItemNum(fullName).ToString();
40                 }
41
42
43             }
44
45             // Save the configuration file.
46             config.Save(ConfigurationSaveMode.Modified);
47
48             // Force a reload of the changed section. This
49             // makes the new values available for reading.
50             ConfigurationManager.RefreshSection(sectionName);

使用appSettings要特别注意，上面代码中config.AppSettings.Settings和appSettings都能够索引到键值，正常读取配置文件之后，两者是一样的，但是，当执行了上面的config.AppSettings.Settings.Clear();之后，两者就不同步了，config.AppSettings.Settings（配置文件里）清空了，但是appSettings（内存里）还有之前的记录，(appSettings[fileName] == null)就不一定为true了，这样直接用config.AppSettings.Settings[fileName].Value添加值，会报null异常。

所以还加了上面19~26行部分代码，而且
appSettings =
ConfigurationManager.AppSettings;
这个给appSettings重新赋值也是必须的。

摘自果壳中的宇宙

补充：软件开发 , C# ,