我试图在我的代码中使用Reflection1示例实现数据转换。
GetSourceValue函数有一个比较各种类型的开关,但我想删除这些类型和属性,并让GetSourceValue只使用一个字符串作为参数来获取属性的值。我想在字符串中传递一个类和属性,并解析属性的值。
这可能吗?
1原始博客文章的Web存档版本
我试图在我的代码中使用Reflection1示例实现数据转换。
GetSourceValue函数有一个比较各种类型的开关,但我想删除这些类型和属性,并让GetSourceValue只使用一个字符串作为参数来获取属性的值。我想在字符串中传递一个类和属性,并解析属性的值。
这可能吗?
1原始博客文章的Web存档版本
当前回答
以下是我根据其他答案得出的结论。把错误处理弄得这么具体,有点过分了。
public static T GetPropertyValue<T>(object sourceInstance, string targetPropertyName, bool throwExceptionIfNotExists = false)
{
string errorMsg = null;
try
{
if (sourceInstance == null || string.IsNullOrWhiteSpace(targetPropertyName))
{
errorMsg = $"Source object is null or property name is null or whitespace. '{targetPropertyName}'";
Log.Warn(errorMsg);
if (throwExceptionIfNotExists)
throw new ArgumentException(errorMsg);
else
return default(T);
}
Type returnType = typeof(T);
Type sourceType = sourceInstance.GetType();
PropertyInfo propertyInfo = sourceType.GetProperty(targetPropertyName, returnType);
if (propertyInfo == null)
{
errorMsg = $"Property name '{targetPropertyName}' of type '{returnType}' not found for source object of type '{sourceType}'";
Log.Warn(errorMsg);
if (throwExceptionIfNotExists)
throw new ArgumentException(errorMsg);
else
return default(T);
}
return (T)propertyInfo.GetValue(sourceInstance, null);
}
catch(Exception ex)
{
errorMsg = $"Problem getting property name '{targetPropertyName}' from source instance.";
Log.Error(errorMsg, ex);
if (throwExceptionIfNotExists)
throw;
}
return default(T);
}
其他回答
在. net Standard中调用的方法已经改变(从1.6开始)。我们还可以使用c# 6的空条件操作符。
using System.Reflection;
public static object GetPropValue(object src, string propName)
{
return src.GetType().GetRuntimeProperty(propName)?.GetValue(src);
}
如果我用Ed s的密码,我就
“ReflectionExtensions。由于其保护级别,GetProperty(Type, string)'不可访问
似乎GetProperty()在Xamarin.Forms中不可用。TargetFrameworkProfile是我的便携式类库中的Profile7。NET Framework 4.5, Windows 8, ASP。NET Core 1.0, Xamarin。Android, Xamarin的。Xamarin的iOS。iOS经典)。
现在我找到了一个可行的解决方案:
using System.Linq;
using System.Reflection;
public static object GetPropValue(object source, string propertyName)
{
var property = source.GetType().GetRuntimeProperties().FirstOrDefault(p => string.Equals(p.Name, propertyName, StringComparison.OrdinalIgnoreCase));
return property?.GetValue(source);
}
源
这样怎么样:
public static Object GetPropValue(this Object obj, String name) {
foreach (String part in name.Split('.')) {
if (obj == null) { return null; }
Type type = obj.GetType();
PropertyInfo info = type.GetProperty(part);
if (info == null) { return null; }
obj = info.GetValue(obj, null);
}
return obj;
}
public static T GetPropValue<T>(this Object obj, String name) {
Object retval = GetPropValue(obj, name);
if (retval == null) { return default(T); }
// throws InvalidCastException if types are incompatible
return (T) retval;
}
这将允许你使用单个字符串进入属性,就像这样:
DateTime now = DateTime.Now;
int min = GetPropValue<int>(now, "TimeOfDay.Minutes");
int hrs = now.GetPropValue<int>("TimeOfDay.Hours");
您可以将这些方法用作静态方法或扩展。
看看Heleonix。反映图书馆。你可以通过路径获取/设置/调用成员,或者创建一个getter/setter (lambda编译成委托),这比反射更快。例如:
var success = Reflector.Get(DateTime.Now, null, "Date.Year", out int value);
或者只创建一个getter并缓存以供重用(这样性能更好,但如果中间成员为空可能会抛出NullReferenceException):
var getter = Reflector.CreateGetter<DateTime, int>("Date.Year", typeof(DateTime));
getter(DateTime.Now);
或者如果你想创建一个List<Action<object, object>>的不同getter,只需要为已编译的委托指定基本类型(类型转换将被添加到已编译的lambdas中):
var getter = Reflector.CreateGetter<object, object>("Date.Year", typeof(DateTime));
getter(DateTime.Now);
jheddings的回答很好。我想通过允许引用聚集的数组或对象的集合来改进它,这样propertyName可以是property1.property2[X].property3:
public static object GetPropertyValue(object srcobj, string propertyName)
{
if (srcobj == null)
return null;
object obj = srcobj;
// Split property name to parts (propertyName could be hierarchical, like obj.subobj.subobj.property
string[] propertyNameParts = propertyName.Split('.');
foreach (string propertyNamePart in propertyNameParts)
{
if (obj == null) return null;
// propertyNamePart could contain reference to specific
// element (by index) inside a collection
if (!propertyNamePart.Contains("["))
{
PropertyInfo pi = obj.GetType().GetProperty(propertyNamePart);
if (pi == null) return null;
obj = pi.GetValue(obj, null);
}
else
{ // propertyNamePart is areference to specific element
// (by index) inside a collection
// like AggregatedCollection[123]
// get collection name and element index
int indexStart = propertyNamePart.IndexOf("[")+1;
string collectionPropertyName = propertyNamePart.Substring(0, indexStart-1);
int collectionElementIndex = Int32.Parse(propertyNamePart.Substring(indexStart, propertyNamePart.Length-indexStart-1));
// get collection object
PropertyInfo pi = obj.GetType().GetProperty(collectionPropertyName);
if (pi == null) return null;
object unknownCollection = pi.GetValue(obj, null);
// try to process the collection as array
if (unknownCollection.GetType().IsArray)
{
object[] collectionAsArray = unknownCollection as object[];
obj = collectionAsArray[collectionElementIndex];
}
else
{
// try to process the collection as IList
System.Collections.IList collectionAsList = unknownCollection as System.Collections.IList;
if (collectionAsList != null)
{
obj = collectionAsList[collectionElementIndex];
}
else
{
// ??? Unsupported collection type
}
}
}
}
return obj;
}