Question

I have a number of classes that are decorated with DebuggerDisplayAttribute.

I want to be able to add trace statements to Unit Tests that will display instances of these classes.

Does there exist a method in the .NET Framework that will display an object formatted using DebuggerDisplayAttribute (or fall back to using .ToString() if no DebuggerDisplayAttribute is defined)?

EDIT

To clarify, I was hoping there might be something built into the Framework. I know I can get the Value property from DebuggerDisplayAttribute, but I then need to format my instance using the format string represented by DebuggerDisplayAttribute.Value.

If I roll my own, I’d envisage an extension method along the following lines:

public string FormatDebugDisplay(this object value)
{
    DebugDisplayAttribute attribute = ... get the attribute for value ...
    if (attribute = null) return value.ToString();

    string formatString = attribute.Value;

    ??? How do I format value using formatString ???
    return SomeFormatMethod(formatString, value);
}

Answer 1

That might be nice — but DebuggerDisplayAttribute’s format string is evaluated by the debugger, the same way it evaluates expressions you type into the Watch windows or the Immediate window. That’s why you can put arbitrary expressions inside the braces, like {FirstName + " " + LastName}.

Therefore, to evaluate these in your code, you would need to embed the Visual Studio debugger into your app. Probably not gonna happen. (grin)

Your best bet is probably to take all the formatting logic that’s currently in your DebuggerDisplay format string, and make it a method instead. Then you’re free to call that method from your code. Your DebuggerDisplay attribute ends up doing nothing but calling the method.

[DebuggerDisplay("{Inspect()}")]
public class MyClass {
    public string Inspect() { ... }
}