I am not entirely sure what kind of data you have bound to your column. That is why I attached a sample project that demonstrates a common scenario with RadGridView. In general if you have a string property bound to the GridViewDataColumn, by default you will have a TextBox as an editor (CellEditTemplate) and a TextBlock as a CellTemplate. So by double clicking on a cell in that column, you will enter edit mode state (the default TextBox) for that cell.
For more information about RadGridView you can refer to our documentation, online demos and sdk examples:
1) Getting Started documentation article.
2) Online Demos.
3) SDK Examples - Although GitHub is a very well-known platform we saw a better and easier approach for reviewing our examples by developing our SDK Samples Browser.
I hope this helps.
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