Hide weekends on WPF toolkit chart
After much playing around with various options, I ended up using the CategoryAxis instead of DateTimeAxis. It treats each day as a category without inferring the relationship between the days.
The data can still be kept as DateTime objects for any necessary calculations and you just have to worry about the ToString (that's what CategoryAxis to label each category). Or just throw them all in as strings - technically calculations are done on the data points, not the array of dates so not much of a loss here...