使用反射我如何可以转换为可空的字符串?
我有以下的code转换到几乎放弃几乎所有值的值类型。有相当多的code以上这种使用IsAssignableFrom等,所以这是最后的手段。
MethodInfo的解析= t.GetMethod(解析,新类型[] {typeof运算(字符串)});
如果(解析!= NULL)
{
对象解析= parse.Invoke(空,新的对象[] {value.ToString()});
返程(T)解析;
}
其他
{
抛出新的InvalidOperationException异常(您指定的值不是有效的+ typeof运算(T)的ToString());
}
在问题出现时,我想转换为可空类型一样长?
显然,长时间?类没有一个分析方法。
我如何从提取解析方法可空的模板的类型?
编辑:
下面是测试我试图传递一个短暂的电池:
[测试]
公共无效ConverterTNullable()
{
Assert.That((int)的1,Is.EqualTo(转换器和所述;?int的> .Convert(1)));
Assert.That((int)的2,Is.EqualTo(转换器和所述;?int的> .Convert(2.0D)));
Assert.That(3,Is.EqualTo(转换器<长> .Convert(3)));
Assert.That((对象)空,Is.EqualTo(转换器<长> .Convert()));
Assert.That((对象)空,Is.EqualTo(转换器<长> .Convert(空)));
Assert.That((对象)空,Is.EqualTo(转换器<长> .Convert(的DBNull.Value)));
Assert.That((长)1,Is.EqualTo(转换器<长> .Convert(1)));
Assert.That((长)2,Is.EqualTo(转换器<长> .Convert(2.0)));
Assert.That((长)3,Is.EqualTo(转换器<长> .Convert(3)));
}
和全功能:
///<总结>
///任何兼容的对象转换为T的一个实例
///< /总结>
///<参数名称=值>要转换的值小于/参数>
///<返回>转换后的值小于/回报>
公共静态牛逼转换(对象的值)
{
如果(值T)
{
返回(T)值;
}
类型t = typeof运算(T);
如果(T == typeof运算(字符串))
{
如果(值是为DBNull ||值== NULL)
{
返回(T)(对象)空;
}
其他
{
返回(T)的(对象)(value.ToString());
}
}
其他
{
如果(值是为DBNull ||值== NULL)
{
返回默认(T);
}
如果(值是字符串和放大器;&安培; string.IsNullOrEmpty((字符串)值))
{
返回默认(T);
}
尝试
{
返回(T)值;
}
赶上(InvalidCastException的)
{
}
如果(Nullable.GetUnderlyingType(T)!= NULL)
{
T = Nullable.GetUnderlyingType(T);
}
MethodInfo的解析= t.GetMethod(解析,新类型[] {typeof运算(字符串)});
如果(解析!= NULL)
{
对象解析= parse.Invoke(空,新的对象[] {value.ToString()});
返程(T)解析;
}
其他
{
抛出新的InvalidOperationException异常(您指定的值不是有效的+ typeof运算(T)的ToString());
}
}
}
解决方案
我加这一点点:
如果(Nullable.GetUnderlyingType(T)!= NULL)
{
T = Nullable.GetUnderlyingType(T);
}
MethodInfo的解析= t.GetMethod(解析,新类型[] {typeof运算(字符串)});
谢谢大家!
How can I convert TO a Nullable from a String using reflection?
I have the following code to convert TO almost any value type given almost any value. There is quite a bit of code above this to use the IsAssignableFrom, etc. so this is the last resort.
MethodInfo parse = t.GetMethod("Parse", new Type[] { typeof(string) });
if (parse != null)
{
object parsed = parse.Invoke(null, new object[] { value.ToString() });
return (T)parsed;
}
else
{
throw new InvalidOperationException("The value you specified is not a valid " + typeof(T).ToString());
}
The problem comes when I want to to convert to a nullable type like long?.
Obviously, the long? class does not have a parse method.
How do I extract the parse method from the nullable's template type?
EDIT:
Here is a short battery of tests I'm trying to pass:
[Test]
public void ConverterTNullable()
{
Assert.That((int?)1, Is.EqualTo(Converter<int?>.Convert(1)));
Assert.That((int?)2, Is.EqualTo(Converter<int?>.Convert(2.0d)));
Assert.That(3, Is.EqualTo(Converter<long>.Convert(3)));
Assert.That((object)null, Is.EqualTo(Converter<long?>.Convert("")));
Assert.That((object)null, Is.EqualTo(Converter<long?>.Convert(null)));
Assert.That((object)null, Is.EqualTo(Converter<long?>.Convert(DBNull.Value)));
Assert.That((long)1, Is.EqualTo(Converter<long?>.Convert("1")));
Assert.That((long)2, Is.EqualTo(Converter<long?>.Convert(2.0)));
Assert.That((long?)3, Is.EqualTo(Converter<long>.Convert(3)));
}
And the whole function:
/// <summary>
/// Converts any compatible object to an instance of T.
/// </summary>
/// <param name="value">The value to convert.</param>
/// <returns>The converted value.</returns>
public static T Convert(object value)
{
if (value is T)
{
return (T)value;
}
Type t = typeof(T);
if (t == typeof(string))
{
if (value is DBNull || value == null)
{
return (T)(object)null;
}
else
{
return (T)(object)(value.ToString());
}
}
else
{
if (value is DBNull || value == null)
{
return default(T);
}
if (value is string && string.IsNullOrEmpty((string)value))
{
return default(T);
}
try
{
return (T)value;
}
catch (InvalidCastException)
{
}
if (Nullable.GetUnderlyingType(t) != null)
{
t = Nullable.GetUnderlyingType(t);
}
MethodInfo parse = t.GetMethod("Parse", new Type[] { typeof(string) });
if (parse != null)
{
object parsed = parse.Invoke(null, new object[] { value.ToString() });
return (T)parsed;
}
else
{
throw new InvalidOperationException("The value you specified is not a valid " + typeof(T).ToString());
}
}
}
解决方案
I added this little bit:
if (Nullable.GetUnderlyingType(t) != null)
{
t = Nullable.GetUnderlyingType(t);
}
MethodInfo parse = t.GetMethod("Parse", new Type[] { typeof(string) });
Thanks everyone!