Normally you should do the validation of your two dates on the client (in the View), so in order to do that you should do the next staps:
1)Define a custom validation attribute class;
2)Mark you both
DateTime
properties from your model with this attribute;
3)Update the view to use validation for both properties by using
@Html.ValidationMessageFor()
.
You can see details here:
https://code.msdn.microsoft.com/Build-Custom-Data-840477b9[
^]