C# ConfigurationManager 类的使用

一、前言

　　在项目中，我们习惯使用 ConfigurationManager 来读取一些常量。如链接数据库字符串、一些需配置的数据（微信、QQ、支付宝）等的配置。我们需要把这些数据记录在 app.config 或者 web.config 中。接下来我们具体看一下 ConfigurationManager  ：

二、介绍

　　　命名空间：System.Configuration

　　　程序集： System.Configuration.dll

　　引用：在使用中，如果出现“ 当前上下文中不存在名称：ConfigurationManager ”，你就要检查有没有引用程序集和命名空间了。

　　ConfigurationManager类： 包含属性（AppSettings、ConnectionStrings ）、方法（GetSection、OpenExeConfiguration、OpenExeConfiguration、OpenMachineConfiguration、OpenMappedExeConfiguration、OpenMappedExeConfiguration、OpenMappedMachineConfiguration、RefreshSection）

三、使用

　　通过 AppSettings 来获取数据，简单使用案例：

using System;
using System.Configuration;  

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            ReadAllSettings();
            ReadSetting("Setting1");
            ReadSetting("NotValid");
            AddUpdateAppSettings("NewSetting", "May 7, 2014");
            AddUpdateAppSettings("Setting1", "May 8, 2014");
            ReadAllSettings();
        }  

        static void ReadAllSettings()
        {
            try
            {
                var appSettings = ConfigurationManager.AppSettings;  

                if (appSettings.Count == )
                {
                    Console.WriteLine("AppSettings is empty.");
                }
                else
                {
                    foreach (var key in appSettings.AllKeys)
                    {
                        Console.WriteLine("Key: {0} Value: {1}", key, appSettings[key]);
                    }
                }
            }
            catch (ConfigurationErrorsException)
            {
                Console.WriteLine("Error reading app settings");
            }
        }  

        static void ReadSetting(string key)
        {
            try
            {
                var appSettings = ConfigurationManager.AppSettings;
                string result = appSettings[key] ?? "Not Found";
                Console.WriteLine(result);
            }
            catch (ConfigurationErrorsException)
            {
                Console.WriteLine("Error reading app settings");
            }
        }  

        static void AddUpdateAppSettings(string key, string value)
        {
            try
            {
                var configFile = ConfigurationManager.OpenExeConfiguration(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)
            {
                Console.WriteLine("Error writing app settings");
            }
        }
    }
}

在文件 App.config 中配置：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
  </startup>
  <appSettings>
    <add key="Setting1" value="May 5,2018"/>
    <add key="Setting2" value="May 5,2017"/>
  </appSettings>
</configuration>

2、通过使用 ConnectionStrings 来获取数据，使用案例

using System;
using System.Configuration;
using System.Data.SqlClient;  

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            ReadUsers();
        }  

        static void ReadUsers()
        {
            var connectionString = ConfigurationManager.ConnectionStrings["Default"].ConnectionString;
            string queryString = "SELECT Id, Name FROM abpusers;";
            using (var connection = new SqlConnection(connectionString))
            {
                var command = new SqlCommand(queryString, connection);
                connection.Open();
                using (var reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        Console.WriteLine(String.Format("{0}, {1}", reader[], reader[]));
                    }
                }
            }
        }
    }
}

在 App.config 中配置数据库链接字符串：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
  </startup>
  <appSettings>
    <add key="Setting1" value="May 5,2018"/>
    <add key="Setting2" value="May 5,2017"/>
  </appSettings>

  <connectionStrings>
    <add name="Default" connectionString="Server=127.0.0.1; Database=CityManage; Trusted_Connection=False; Uid=root; pwd=zxx123456;" providerName="System.Data.SqlClient" />
    <add name="Abp.Redis.Cache" connectionString="localhost" />
  </connectionStrings>

</configuration>

简单小节，资源来源于：官网教程