深结构类的equals()为.NET类?
-
22-08-2019 - |
题
给定两个反对,认为不包含在其中的参考循环,你知道,在测试一个“通用”的方式他们的平等(通过反射)的方法?
我基本上要相同的语义结构等价,仅在类。
解决方案
我觉得这是在框架中没有可用这样的方法,但它很容易写的。也许不是最短的实现,但似乎做的工作:
private bool AreEqual(object x, object y)
{
// if both are null, they are equal
if (x == null && y == null)
{
return true;
}
// if one of them are null, they are not equal
else if (x == null || y == null)
{
return false;
}
// if they are of different types, they can't be compared
if (x.GetType() != y.GetType())
{
throw new InvalidOperationException("x and y must be of the same type");
}
Type type = x.GetType();
PropertyInfo[] properties = type.GetProperties();
for (int i = 0; i < properties.Length; i++)
{
// compare only properties that requires no parameters
if (properties[i].GetGetMethod().GetParameters().Length == 0)
{
object xValue = properties[i].GetValue(x, null);
object yValue = properties[i].GetValue(y, null);
if (properties[i].PropertyType.IsValueType && !xValue.Equals(yValue))
{
return false;
}
else if (!properties[i].PropertyType.IsValueType)
{
if (!AreEqual(xValue, yValue))
{
return false;
}
} // if
} // if
} // for
return true;
}
其他提示
如果你想这样做的无在每次调用做反射,你可能要考虑建立在第一次调用一个DynamicMethod
和使用代替。 (我有一个链接,这是否与文章,但我失去了它 - 对不起 - 尝试,如果有兴趣的谷歌搜索)
顺便说一句
Expression.Lambda<Func<T,T,bool>> Compile()
可以作为一个动态方法助洗剂。
仍然有在构建Expresison使用反射
下面是从弗雷德里克·莫克的答案的更新版本,考虑到Nullable
和递归引用:
public static bool AreEqual<T>(T x, T y) =>
AreEqual(x, y, new HashSet<object>(new IdentityEqualityComparer<object>()));
private static bool AreEqual(object x, object y, ISet<object> visited)
{
// if both are null, they are equal
if (x == null && y == null) return true;
// if one of them are null, they are not equal
if (x == null || y == null) return false;
// if they are of different types, they can't be compared
if (x.GetType() != y.GetType())
{
throw new InvalidOperationException("x and y must be of the same type");
}
// check for recursive references
if (visited.Contains(x)) return true;
if (visited.Contains(y)) return true;
visited.Add(x);
visited.Add(y);
var type = x.GetType();
var properties = type.GetProperties();
foreach (var property in properties)
{
// compare only properties that requires no parameters
if (property.GetGetMethod().GetParameters().Length == 0)
{
object xValue = property.GetValue(x, null);
object yValue = property.GetValue(y, null);
if (property.PropertyType.IsValueType)
{
// check for Nullable
if (xValue == null && yValue == null) continue;
if (xValue == null || yValue == null) return false;
if (!xValue.Equals(yValue)) return false;
}
if (!property.PropertyType.IsValueType)
{
if (!AreEqual(xValue, yValue, visited)) return false;
}
}
}
return true;
}
private class IdentityEqualityComparer<T> : IEqualityComparer<T> where T : class
{
public int GetHashCode(T value) => RuntimeHelpers.GetHashCode(value);
public bool Equals(T left, T right) => left == right;
}
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