Question

我尝试从自定义配置文件访问配置项，但收到错误CS0122。

类别：

using System;
using System.IO;
using System.Configuration;
using System.Windows.Forms;

public class SaveLoadSettings
{
    private static string path = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.CommonApplicationData), "XMLConverterForTelekomInvoice", "XMLConverterForTelekomInvoice.config");
}

写入设置的功能:(这很好用）

    private static void AddUpdateAppSettings(string key, string value)
    {
        try
        {
            var configFile = ConfigurationManager.OpenMappedExeConfiguration(new ExeConfigurationFileMap { ExeConfigFilename = path }, ConfigurationUserLevel.None);
            var settings = configFile.AppSettings.Settings;
            if (settings[key] == null)
            {
                settings.Add(key, value);
            }
            else
            {
                settings[key].Value = value;
            }
            configFile.Save(ConfigurationSaveMode.Modified);
            ConfigurationManager.RefreshSection(configFile.AppSettings.SectionInformation.Name);
        }
        catch (ConfigurationErrorsException)
        {
            MessageBox.Show("Error writing app settings");
        }
    }

读取设置的功能:(在appSettings [key]上生成CS0122）

    private static string ReadSetting(string key)
    {
        try
        {
            Configuration MyAppConfig = ConfigurationManager.OpenMappedExeConfiguration(new ExeConfigurationFileMap { ExeConfigFilename = path }, ConfigurationUserLevel.None);
            var appSettings = MyAppConfig.AppSettings;
            string result = appSettings[key] ?? string.Empty;
            return result;
        }
        catch (ConfigurationErrorsException)
        {
            MessageBox.Show("Error reading app settings");
            return string.Empty;
        }
    }

XML文件：

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <appSettings>
        <add key="Setting1" value="25" />
        <add key="Setting2" value="10" />
    </appSettings>
</configuration>

我是编码方面的新手，我无法弄清楚代码中的问题是什么。也许有些人可以帮助我。问候kami

我在更改某些代码时遇到的问题：

string result = appSettings.Settings[key] ?? string.Empty; // Generates CS0019 ?? Operator can't be used on KeyValueConfigurationElement
string result = appSettings.Settings[key].ToString() ?? string.Empty; // Throws "System.NullReferenceException" in Runtime

Answer 1

编译器抱怨这一行：string result = appSettings[key] ?? string.Empty;，具体而言，appSettings[key]由于其保护级别而无法访问。

要从自定义.config文件中提取设置值，您可以使用appSettings实例上的Settings属性：

private static string ReadSetting(string key)
    {
        try
        {
            Configuration MyAppConfig = ConfigurationManager.OpenMappedExeConfiguration(new ExeConfigurationFileMap { ExeConfigFilename = path }, ConfigurationUserLevel.None);
            var appSettings = MyAppConfig.AppSettings;
            string result = appSettings.Settings[key].Value ?? string.Empty; // ** change here
            return result;
        }
        catch (ConfigurationErrorsException)
        {
            MessageBox.Show("Error reading app settings");
            return string.Empty;
        }
    }

编辑：固定代码（缺少.Value）

Answer 2

这是我解决问题的方法：

private static string ReadSettingString(string key)
{
    try
    {
        Configuration MyAppConfig = ConfigurationManager.OpenMappedExeConfiguration(new ExeConfigurationFileMap { ExeConfigFilename = path }, ConfigurationUserLevel.None);
        var appSettings = MyAppConfig.AppSettings;
        string result = appSettings?.Settings?[key]?.Value ?? string.Empty;
        return result;
    }
    catch (ConfigurationErrorsException)
    {
        MessageBox.Show("Error reading app settings");
        return string.Empty;
    }
}

感谢你的帮助Steve Wong

在Custom.Configuration文件中访问AppSettings（CS0122）

2 个答案: