C# Dynamic Dictionary - Selecting Random Value from Dynamic Object

I've been exploring dynamic dictionaries as a potential solution to associating multiple strings with a single 'ID' string. What I need to do is assign a series of 4-letter text strings to a key that is also a 4-letter text string (each string is unique with a range of AAAA-ZZZZ).

The keys are 4-letter text strings like: "AAAA", "AAGB", etc. Each key can hold multiple 4-letter text strings: "ACFE", "AAFE", etc.

The goal is to select a key and then randomly select one of the dynamic values inside it. My current setup for testing is as follows:

        dynamic d1 = new System.Dynamic.ExpandoObject();  // Dynamic objects
        dynamic d2 = new System.Dynamic.ExpandoObject();
        dynamic d3 = new System.Dynamic.ExpandoObject();

        var dict = new Dictionary<string, dynamic>();
        // Assign dynamic objects to the Dictionary Key
        dict["AAAA"] = d1;
        dict["AAGB"] = d2;
        dict["ABDA"] = d3;

        // Populate the dynamic object with the value(s)
        dict["AAAA"].FooBar = new { i1 = "ACFE", i2 = "AAFE", i3 = "CAED", i4 = "HSGB" };
        dict["AAGB"].FooBar = new { i1 = "ZZZZ", i2 = "XXXX", i3 = "CAED", i4 = "HSGB" };
        dict["ABDA"].FooBar = new { i1 = "YYYY", i2 = "WWWW", i3 = "CAED", i4 = "HSGB" };

        string newName = dict["ABDA"].FooBar.i1;
        return newName;

That pulls through the correct string. But is there a way of setting this up so I can pull one of the values out at random instead of having to explicitly specify which value I'm after? Or should I change approach altogether (I've done something similar to this using jagged arrays and will use that as a fallback but was curious about this dynamic dictionary as a possible alternative).