There is a known issue with setting a textbox to be multiline and we are working on fixing it. However, as a workaround I may propose to you to use the property of GridViewDataColumn called EditorStyle which allows you to customize the editor being used. For example:
I am sending you a sample project so that you can see and test the proposed solution. Furthermore, a example with the usage of ListBox is included.
I hope that helps, but in case this does not meet exactly your requirements, please do not hesitate to get back to us.
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