Get property value to use within custom attribute

Question

I have been looking for an example of how to get a property's value from within a custom attribute's code.

Example for illustration purposes only: We have a simple book class with only a name property. The name property has a custom attribute:

public class Book { [CustomAttribute1] property Name { get; set; } }

Within the custom attribute's code, I would like to get the value of the property on which the attribute has been decorated:

public class CustomAttribute1: Attribute { public CustomAttribute1() { //I would like to be able to get the book's name value here to print to the console: // Thoughts? Console.WriteLine(this.Value) } }

Of course, "this.Value" does not work. Any thoughts?

Well it depends of your use case, sometimes its easier just to use CustomAttribute[name="something"]. But I think you should use reflection if you want, what you want. have a look at stackoverflow.com/questions/6637679/… — madz
– madz, Commented Feb 25, 2015 at 8:00
Actually, that is the opposite of what I am looking for (the above link allows for finding properties where an attribute has been provided, and you get the name and value). What I am looking for is once the CustomAttribute code is called, the CustomAttribute code knows that it was called from the name property and can detect the property's value. If I could detect the class name and property name from within CustomAttribute, I could use Reflection to get the value, but I can't seem to do that. — Tom Atwood
– Tom Atwood, Commented Feb 25, 2015 at 23:04
What do you want to achieve, and why do you think that attributes is the right way to do that? — user4003407
– user4003407, Commented Feb 25, 2015 at 23:52

Tom Atwood · Accepted Answer · 2015-02-25 23:32:17Z

OK, I figured it out. This is only available with .Net 4.5 and later though.

In the System.Runtime.CompilerServices library, there is a CallerMemberNameAttribute class available. To get the name of the calling class, there is a CallerFilePathAttribute class that returns the full path of the calling class for later use with Reflection. Both are used as follows:

public class CustomAttribute1: Attribute { public CustomAttribute1([CallerMemberName] string propertyName = null, [CallerFilePath] string filePath = null) { //Returns "Name" Console.WriteLine(propertyName); //Returns full path of the calling class Console.WriteLine(filePath); } }

I hope you find this as helpful in your work.

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