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.

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.

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.

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

The SUMIFS function adds all of its arguments that meet multiple criteria.

A list of the supported functions is available at http://docs.telerik.com/devtools/document-processing/libraries/radspreadprocessing/features/formulas/functions

This function can be implemented as a custom function. Check the following resources for more details on how to achieve that:

- http://docs.telerik.com/devtools/document-processing/libraries/radspreadprocessing/features/formulas/custom-functions
- https://github.com/telerik/xaml-sdk/tree/master/Spreadsheet/WPF/CustomFunctions

- Async parse of single xml file to speed-up the import
- Allow to import only part of the file
- Respect the widths of the columns and row heights and do not measure them first time in the WorksheetLayout or measure them for the current Viewport only
- Inserting rows/columns also need improvements in terms of performance.

The class would be used for customization of the printing behavior of the control.

Implement automatic completion of cell value based on the values typed above, in the same column.

Through the sorting options, the user can set sort orientation (to sort by rows or by columns) and whether the sort should be case sensitive.

Add support for formats which can present numbers with non-arabic numerals, for example:
 
- Bengali - [$-bn-IN,500]0
- Devanagari - [$-hi-IN,400]0
- East Arabic - [$-ar-SA,200]0
- Persian - [$-ar-SA,300]0
- Gujarati - [$-gu-IN,700]0
- Kannada - [$-kn-IN,B00]0
- Khmer - [$-et-EE,1200]0
- Lao - [$-lo-LA,E00]0
- Malayalam - [$-ml-IN,C00]0
- Mongolian - [$-mn-MN,1300]0
- Burmese - [$-my-MM,1000]0
- Oriya - [$-or-IN,800]0
- Tamil - [$-ta-IN,900]0
- Telugu - [$-te-IN,A00]0
- Thai - [$-th-TH,D00]0
- Tibetan - [$-bo-CN,F00]0

Currently, the customers can bind data only to the Workbook property of RadSpreadsheet. Allow them binding cell range to a data source.

COUNTA function is similar to COUNTIF function, but it only counts the non-empty cells. 

Description from Microsoft here: https://support.office.com/en-us/article/COUNTA-function-7dc98875-d5c1-46f1-9a82-53f3219e2509?ui=en-US&rs=en-US&ad=US&fromAR=1 .

Workaround: it should be possible to implement such custom function. See Custom Functions help article here: http://docs.telerik.com/devtools/document-processing/libraries/radspreadprocessing/features/formulas/custom-functions .

When using the Fill feature through the dialog, the series are currently filled only for the cells, which are included in the selection. Introduce functionality to fill them without requiring a selection.

A custom implementation can be plugged through a custom dialog. A sample showing how to replace the default dialog with a custom one is available in the attachments of the item.

Provide the ability to work with images in headers/footers of a worksheet. Note that large images put in headers are visualized as watermarks on printing/exporting to PDF.

At this point, the ribbon and the context menu are not localized out of the box and the users need to change the strings manually.

Currently the following text filters are not supported in the model, filtering popup and Custom Filter dialog:
- begins with
- does not begin with
- ends with
- does not end with
- contains
- does not contain.

All of these are supported in MS Excel.

Add support for import and export of Excel Template files (XLTS) file format.