C# – Get all properties with values reflection

.netc++reflection

I wrote custom property attribute and set it on couple of properties in my class. Now I would like during runtime get only properties which has this attribute, be able to get value of the property as well as values of attribute fields. Could You please help me with this task ?
thanks for help

Best Solution

Here's an example:

void Main()
{
    var myC = new C { Abc = "Hello!" };
    var t = typeof(C);
    foreach (var prop in t.GetProperties())
    {
        var attr = prop.GetCustomAttributes(typeof(StringLengthAttribute), true).Cast<StringLengthAttribute>().FirstOrDefault();
        if (attr != null)
        {
            var attrValue = attr.MaximumLength; // 100
            var propertyValue = prop.GetValue(myC, null); // "Hello!"
        }
    }
}
class C
{
    [StringLength(100)]
    public string Abc {get;set;}
}

Related Solutions

Java – reflection and why is it useful

The name reflection is used to describe code which is able to inspect other code in the same system (or itself).

For example, say you have an object of an unknown type in Java, and you would like to call a 'doSomething' method on it if one exists. Java's static typing system isn't really designed to support this unless the object conforms to a known interface, but using reflection, your code can look at the object and find out if it has a method called 'doSomething' and then call it if you want to.

So, to give you a code example of this in Java (imagine the object in question is foo) :

Method method = foo.getClass().getMethod("doSomething", null);
method.invoke(foo, null);

One very common use case in Java is the usage with annotations. JUnit 4, for example, will use reflection to look through your classes for methods tagged with the @Test annotation, and will then call them when running the unit test.

There are some good reflection examples to get you started at http://docs.oracle.com/javase/tutorial/reflect/index.html

And finally, yes, the concepts are pretty much similar in other statically typed languages which support reflection (like C#). In dynamically typed languages, the use case described above is less necessary (since the compiler will allow any method to be called on any object, failing at runtime if it does not exist), but the second case of looking for methods which are marked or work in a certain way is still common.

Update from a comment:

The ability to inspect the code in the system and see object types is not reflection, but rather Type Introspection. Reflection is then the ability to make modifications at runtime by making use of introspection. The distinction is necessary here as some languages support introspection, but do not support reflection. One such example is C++

C# – Create Generic method constraining T to an Enum

Since Enum Type implements IConvertible interface, a better implementation should be something like this:

public T GetEnumFromString<T>(string value) where T : struct, IConvertible
{
   if (!typeof(T).IsEnum) 
   {
      throw new ArgumentException("T must be an enumerated type");
   }

   //...
}

This will still permit passing of value types implementing IConvertible. The chances are rare though.

Best Solution

Related Solutions

Java – reflection and why is it useful

C# – Create Generic method constraining T to an Enum

Related Question