I have form with calender control and a dropdownlist and when user has selected data for both controls I call a custom method which must use the data from both these controls. Can you tell me how to do it and how to get access to the controls data in the custom method?
You need to set the Value property of the components to a page property. Then use those properties when setting the parameters of the custom method. The following resources would be of help:
You say I need to set the Value property of the component to the page property I just created. But the Calendar control does not have a Value property. So where do I connect the page property to the Calendar control?
Radzen doesn't have a Calendar component and I thought you meant the DatePicker which as a Value property. What component are you actually using?
I should have been more clear 
I am using form and the datatype is date. So it is here I want to put the selected date into a property and use it in custom method.