ToPropertyPath.cs

public static string ToPropertyPath<TB, T>(this Expression<Func<TB, T>> func)
{
    var result = new StringBuilder();
    var node = func.Body;
    while (node.NodeType == ExpressionType.MemberAccess)
    {
        var me = node as MemberExpression;
        if (result.Length != 0) result.Insert(0, ".");
        result.Insert(0, me.Member.Name);
        node = me.Expression;
    }
    return result.ToString();
}