如何解决此问题,以将其通用转换为Nullable< T> ;? [英] How can I fix this up to do generic conversion to Nullable<T>?
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问题描述
我目前使用这种方便的转换扩展方法在类型之间进行转换:
I currently use this handy conversion extension method to do conversions between types:
public static T To<T>(this IConvertible obj)
{
return (T)Convert.ChangeType(obj, typeof(T));
}
但是,它不喜欢将有效值转换为Nullable,例如,这会失败:
However, it doesn't like converting valid values to Nullable, for example, this fails:
"1".To<int?>();
显然,很容易将1转换为(int?),但是会出现错误:
Obviously, 1 is easily converted to an (int?), but it gets the error:
Invalid cast from 'System.String' to 'System.Nullable`1[[System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]'.
这是一个明显简化的示例,实际上我正在使用它来进行类似字符串类型的转换因此:
This is an obviously simplified example, in reality I'm using it to do conversions from string types like so:
packageDb.Quantity = package.package.ElementDeep(Namespace + "PackageQuantity", Namespace + "ActualQuantity", Namespace + "Quantity").ValueOrNull().To<int?>();
如果Convert.ChangeType不喜欢Nullable,那么有人有什么好主意吗?
If Convert.ChangeType doesn't like Nullable, anyone have any great ideas?
推荐答案
public static T To<T>(this IConvertible obj)
{
Type t = typeof(T);
Type u = Nullable.GetUnderlyingType(t);
if (u != null)
{
return (obj == null) ? default(T) : (T)Convert.ChangeType(obj, u);
}
else
{
return (T)Convert.ChangeType(obj, t);
}
}
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