In my page type, I have two fields Theme and Branding
I want to set value of Branding based on Theme on Content Creation.
I am trying to do this in SetDefaultValues method but it's not working
You can set the default value of the second property on the Page save/create/publish the event. Like below example
Here is a commonly referenced blog that demonstrates dependent drop-down lists.https://world.episerver.com/blogs/Duong-Nguyen/Dates/2014/1/Country-Region-drop-down-lists-in-All-properties-mode/Its important to note that newer versions of Episerver have changed things a bit, so please make sure you read the newer Comments in that Blog post, and refer to this Forum post. https://world.episerver.com/forum/developer-forum/-Episerver-75-CMS/Thread-Container/2017/4/linked-dropdown-does-not-display-value/Hope this helps.