RadGridView supports data binding to a single DataSource collection at a time. If the AutoGenerateColumns property is set to true, the columns will be generated from the data source.
Every next setting to a new DataSource collection will re-generate the columns according to the columns available in this new DataSource. Appending with the previous DataSource is not expected to be supported.
The possible solution that I can suggest is to append the DataSource programmatically and then apply it to the RadGridView.DataSource property, e.g. if you have DataTable1 and DataTable2 you can create a third DataTable which contains the columns from both DataTable objects and populate the rows considering the cells from both tables.
I hope this information helps. If you need any further assistance please don't hesitate to contact me.
Dess | Tech Support Engineer, Sr.
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