I am sending you a simple working application which demonstrates how to achieve the desired functionality. Please check it out and let me know if it works for you or if I am leaving something important out.
You could also refer to the following example which elaborates on this subject:
Binary Images and Upload in Grid
Additionally, I suggest you examine the following online resources for more information about how to validate the uploaded files.
Validating using an ASP.NET validator
Require at least one file to be uploaded
I hope this helps.
the Telerik team
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