给 IConfiguration 写一个 GetAppSetting 扩展方法
給?IConfiguration?寫一個?GetAppSetting?擴展方法
Intro
在 .net core 中，微軟已經默認使用 appsettings.json 來代替 app.config，并重新設計了一套完整的配置系統，可以支持 json/xml/ini/環境變量等。
在 .net core 中有一個 GetConnectionString 的擴展方法用來比較方便的獲取鏈接字符串，類似于在 .net framework 中使用 ConfigurationManager.ConnectionStrings["key"] 來獲取鏈接字符串。
這次來參考 GetConnectionString 實現一個 GetAppSetting，類似于 .net framework 中使用 ConfigurationManager.AppSettings 來獲取配置值。
實現代碼
GetConnectionString 是獲取 ConnectionStrings 這個節點下的某個配置， GetAppSetting 來獲取 AppSettings 這個節點下的某個配置
實現代碼：
/// <summary>
/// GetAppSetting
/// Shorthand for GetSection("AppSettings")[key]
/// </summary>
/// <param name="configuration">IConfiguration instance</param>
/// <param name="key">appSettings key</param>
/// <returns>app setting value</returns>
public static string GetAppSetting([NotNull]this IConfiguration configuration, string key)
{
return configuration.GetSection("AppSettings")[key];
}
/// <summary>
/// GetAppSetting
/// Shorthand for GetSection("AppSettings")[key]
/// </summary>
/// <param name="configuration">IConfiguration instance</param>
/// <param name="key">appSettings key</param>
/// <returns>app setting value</returns>
public static T GetAppSetting<T>([NotNull]this IConfiguration configuration, string key)
{
return configuration.GetSection("AppSettings")[key].To<T>();
}
/// <summary>
/// GetAppSetting
/// Shorthand for GetSection("AppSettings")[key]
/// </summary>
/// <param name="configuration">IConfiguration instance</param>
/// <param name="key">appSettings key</param>
/// <param name="defaultValue">default value if not exist</param>
/// <returns>app setting value</returns>
public static T GetAppSetting<T>([NotNull] this IConfiguration configuration, string key, T defaultValue)
{
return configuration.GetSection("AppSettings")[key].ToOrDefault(defaultValue);
}
/// <summary>
/// GetAppSetting
/// Shorthand for GetSection("AppSettings")[key]
/// </summary>
/// <param name="configuration">IConfiguration instance</param>
/// <param name="key">appSettings key</param>
/// <param name="defaultValueFunc">default value func if not exist to get a default value</param>
/// <returns>app setting value</returns>
public static T GetAppSetting<T>([NotNull] this IConfiguration configuration, string key, Func<T> defaultValueFunc)
{
return configuration.GetSection("AppSettings")[key].ToOrDefault(defaultValueFunc);
}
查看源碼
使用
使用起來和 GetConnectionString 差不多
測試 appsettings.json
{
"ConnectionStrings": {
"TestDb": "server=.;database=Test;uid=weihanli;pwd=Admin888"
},
"AppSettings":{
"Number": 12,
"City": "Shanghai"
}
}
GetAppSetting 示例
IConfiguration configuration = new ConfigurationBuilder()
// ...
.AddJsonFile("appsettings.json")
.Build();
var city = configuration.GetAppSetting("City");
var number = configuration.GetAppSetting<int>("Number");
System.Console.WriteLine($"City:{city}, Number:{number}");
總結
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