What is the best way to dump entire objects to a log in C#?

For a larger object graph, I second the use of Json but with a slightly different strategy. First I have a static class that is easy to call and with a static method that wraps the Json conversion (note: could make this an extension method).

using Newtonsoft.Json;

public static class F
{
    public static string Dump(object obj)
    {
        return JsonConvert.SerializeObject(obj);
    }
}

Then in your Immediate Window,

var lookHere = F.Dump(myobj);

lookHere will auto-show up in the Locals window prepended with a $ or you can add a watch to it. On the right hand side of the Value column in the inspector, there is a magnifying glass with a dropdown caret beside it. Choose the dropdown caret and choose Json visualizer.

I am using Visual Studio 2013.

You could base something on the ObjectDumper code that ships with the Linq samples.
Have also a look at the answer of this related question to get a sample.