Merging anonymous types

How can I merge two anonymous types, so that the result contains the properties of both source objects?

var source1 = new
{
    foo = "foo",
    bar = "bar"
}

var source2 = new
{
    baz = "baz"
}

var merged = Merge(source1, source2) // <-- here's where the magic should happen

// merged: 
// {
//      foo = "foo",
//      bar = "bar",
//      baz = "baz"
// }