First of all I do not recommend you to re-create your Grid each type you type into an input element - you can just change the data used by the dataSource.
We are not sure what exactly goes wrong with your code, however I re-created similar example to your, the difference is that there is no async call, however there should not be any difference.
Feel free to modify the link and share it if you face any particular difficulties.
the Telerik team
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