The UpdateSource() will not work in your case because the problem is in the fact that the value of the DatePicker is not updated until focus is lost
key is pressed.
We have not provided a way to manually update the Value of the DatePicker. There is a method for this, but it is not publicly visible. If this is an issue for you, we will fix this and send you an update (or you can wait until the next Service Pack in January.
Unfortunately I connot think of a workaround for this.
Thanks for pointing the problem with the IsFocused property. This is a bug and we will look into it. Your Telerik Points have been updated for your involvement.
the Telerik team
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