How do I check enum property when the property is obtained from dynamic in C#?

Question

Suppose I know that property Color of an object returns an enumeration that looks like this one:

enum ColorEnum {
   Red,
   Green,
   Blue
};

and I want to check that a specific object of unknown type (that I know has Color property) has Color set to Red. This is what I would do if I knew the object type:

ObjectType thatObject = obtainThatObject();
if( thatObject.Color == ColorEnum.Red ) {
   //blah
}

The problem is I don't have a reference to the assembly with ColorEnum and don't know the object type.

So instead I have the following setup:

dynamic thatObject = obtainThatObject();

and I cannot cast because I don't know the object type (and the enum type). How should I check the Color?

if( thatObject.Color.ToString() == "Red" ) {
    //blah
}

does work but it looks like the worst examples of cargo cult code I've seen in "The Daily WTF".

How do I do the check properly?

Answer 1

In the side assembly:

enum ColorEnum
{
    Red,
    Green,
    Blue
};

We know that Red exists, but nothing about other colors. So we redefine the enum in our assembly with known values only.

enum KnownColorEnum // in your assembly
{
    Red
};

Therefore we can perform parsing:

public static KnownColorEnum? GetKnownColor(object value)
{
    KnownColorEnum color;

    if (value != null && Enum.TryParse<KnownColorEnum>(value.ToString(), out color))
    { return color; }

    return null;
}

Examples:

// thatObject.Color == ColorEnum.Red
// or
// thatObject.Color == "Red"
if (GetKnowColor(thatObject.Color) == KnownColorEnum.Red) // true
{ }

// thatObject.Color == ColorEnum.Blue
if (GetKnowColor(thatObject.Color) == KnownColorEnum.Red) // false
{ }