The functionality would allow to zoom the print preview and scroll the resulting viewport.

A partial implementation of the zooming functionality can be found in the attached file to provide a starting point for a custom implementation.

The PrintPreviewControl refreshes its preview content on change in the SheetPageSetup object. This method would allow on-demand update.

At the moment this can be achieved by changing something in the page setup and restoring it. 

bool printGridlines = this.spreadsheet.Workbook.ActiveWorksheet.WorksheetPageSetup.PrintOptions.PrintGridlines;
this.spreadsheet.Workbook.ActiveWorksheet.WorksheetPageSetup.PrintOptions.PrintGridlines = !printGridlines;
this.spreadsheet.Workbook.ActiveWorksheet.WorksheetPageSetup.PrintOptions.PrintGridlines = printGridlines;

This behavior happens at a specific width of the cell's Column. Using different VerticalAlignment (not Bottom) would workaround this issue.

In MS Excel, the users can choose between showing the original size of the page and fit it in the window. Expose a similar option in RadSpreadsheet as well.

When the users click on the More Borders option provided in the ribbon UI, the Format Cells dialog opens but the popup of the dropdown is still kept open.

Currently, to change the title of the ribbon, the users need to replace RadSpreadsheetRibbon with its XAML code. Expose a property allowing to do this change directly from RadSpreadsheetRibbon.

When the InsertFunctionDialog is opened and the "Go" button is pressed with many words entered in the search terms field, the performance is so slow that the application appears hanged.

Allow loading of dialogs (SpellCheckAllAtOnce and SpellCheckWordByWord) different than the default ones through MEF. 

Use-cases: set different Width and Height, hide buttons (e.g. AddToDictionary), etc. 

In MS Excel, the users have the option to specify that the data contains a header row. When this option is enabled, the first row of the column is not included in the sorted range. Implement this option in RadSpreadsheet as well.

Currently, changing the sheets performs heavy calculations on the UI thread. This does not allow to perform any other UI task and the busy indicator cannot be shown before all layers are rendered.

An ArgumentNullException is thrown when you try to open a document containing relationship namespace declared in the tag.

<sheet name="Management Position View" sheetId="1" d3p1:id="rId1" xmlns:d3p1="http://schemas.openxmlformats.org/officeDocument/2006/relationships" />

The exception is thrown in the QuarterAutoFillGenerator TryParse method due to the unexpected length of the value.

Workaround: Do not use SetValueAsText method by passing an empty string to it. Use SetValue or ClearValue instead.

At the moment the theme of the RadSpreadsheetRibbon can be set only by setting the theme of the entire application. The individual setting (using telerik:StyleManager.Theme="Windows8") should also be supported.

When the size of the columns is changed using the ColumnSelection.SetWidth(*) method does not update the layout, so subsequent uses of the layout are not calculated correctly. For example BringIntoView method works incorrectly. 

Workaround: call RadSpreadsheet.UpdateLayout() after setting the width.

Cell borders below the cells filled with data are not exported to XLSX.

When a sheet that has a new line in a text value is exported and the resulting file is opened in Excel, the value is displayed without a new line. If you enter edit mode and then exit (without confirming the value by pressing enter) the new line will appear. The reason for this behavior is that when there is a new line in a text value Excel automatically applies wrap text on the cell while RadSpreadsheet does not do that. A possible workaround is to apply wrap text on new values with new line in them.

Implement mechanism for disabling, enabling or changing of the commands of the CellEditor classes, like Copy and Paste.

When filtering a big range of values, the performance is low. The whole UI is re-created.

The exception is thrown when the color for the borders has been previously set using the colors from the predefined palette. The next attempt to set a border color using the ShowMoreColorsDialog leads to error. A message appears to the user saying "Specified cast is not valid".