One of the first entries we would like to make is in regards to a recently added, but pretty useful property: the columnWidthMode. This property is available on the ExtendedDataGridColumn and ExtendedAdvancedDataGridColumn. The idea is this: Let's say you have a DataGrid, with a few columns that always need to be a certain fixed width (for example a checkbox column, or a column that contains an image, or static text). You set the columnWidthMode of this column to "fixed" (default) and then use the "width" property to specify explicitly what the width is supposed to be. Then there are a few columns that contain dynamic text, and you wish the width of the column to match the longest string in the column. You can set the columnWidthMode to "fitToContent" to acheive this. Once the "fixed" and "fitToContent" columns are given their requested widths, rest of the columns get the REMAINING space. You can control this on basis of percentages. You set the columnWidthMode of these columns to "percent", and allocate a "percentWidth" property to each. The caveat is, all columns that have the columnWidthMode property set to "percent", the "percentWidth" needs to add up to a 100.  

Consider a 5 Column Flex Grid:

Column 1: columnWidthMode=fixed, width=20
Column 2: columnWidthMode=fitToContent
Column 3,4,5: columnWidthMode=percent, percentWidth=33.33 each

This should produce a grid that has the first column fixed at 20px, second column dynamic based on what is being displayed, and the last three columns at equal width (1/3rd) of the remaining width on the grid each).