We are working on implementing exporting to Excel in our application's radgridview - we used this tutorial: https://docs.telerik.com/devtools/wpf/controls/radgridview/export/generic/export and it works with some errors.
When trying to create a file with an .xls file extension, we get an error of "The format and extension of this file do not match". How do we fix this?
When saving, the file extension appears twice after the "Excel files" in the save dialog. Why is this? Is this potentially causing issues?
Also, we would like to change the formatting of the file on export - for example, freezing the headers, automatically setting the column widths, etc - what is the best way to set these properties?