Hi sam Aryan,
When you place a RadGridView inside a ScrollViewer, the grid will be measured with infinity. This is why when you are using Width="*", you get this long scroll bar.
You may reference this help link about RadGridView performance
In order to avoid this problem, you may:
1. Use a fixed size to GridView's width
2. Do not use "*" for the column width
3. Do not use ScrollViewer
I hope that this answers your question.
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