在C#中将string.Empty转换为(generic)T? [英] Cast string.Empty to (generic) T in C#?
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问题描述
我有一个实用程序方法,它从旧的 .INI
配置类型文件中返回一个强类型值,并带有签名
内部静态T GetIniSetting< T>(string config,string key,T defVal = default(T))
我希望字符串是特殊的,因为我希望 defaultValue 的默认值为 string.Empty
,而不是默认(字符串)
(即null),在编码器未指定默认值的情况下。
if(cantFindValueInIniFile == true)
{
if((typeof(T)== typeof(string))& &(defaultValue == null))
{
// ***此处需要的代码 - 无法将字符串转换为< T> ***
return(T)string.Empty;
}
return defaultValue;
}
我已经试过硬铸造了,作为
解决方案
'hacky'的方式:
return(T)(object)string.Empty;
注意:
I have a utility method which returns a strongly typed value from an old .INI
configuration type file, with the signature
internal static T GetIniSetting<T>(string config, string key, T defVal = default(T))
I want strings to be special, in that I would like the default value for defaultValue to be string.Empty
, not default(string)
(i.e. null), in the case when the coder hasn't specified a default value.
if (cantFindValueInIniFile == true)
{
if ((typeof(T) == typeof(string)) && (defaultValue == null))
{
// *** Code needed here - Cannot convert string to <T>***
return (T)string.Empty;
}
return defaultValue;
}
I've tried hard casting, and the as
keyword, to no avail.
解决方案
The 'hacky' way:
return (T)(object)string.Empty;
Notes:
- Pretty safe as you have check pre-conditions.
- Performance penalty unnoticeable on reference types.
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