row autosize based on single column

Hi Bob,

I've been looking into this issue and it's actually much more complicated than it seems.

This is actually not a new issue. I went all the way back to NetAdvantage v8.1 and it was happening all the way back then and probably before. This begs the question of why no one ever noticed it before. The answer is that the issue only happens under some very specific and rare circumstances with a very specific combination of properties.

It doesn't necessarily occur when there is extra space for more rows in the grid. If you change your sample so that there are only 4 rows instead of 5, the problem does not occur. In fact, the problem does not occur with 1, 2, or 3 rows, either.

The issue actually occurs when autosizing a row causes that row to increase in size such that the grid needs a vertical scrollbar where it did not need one before. Presumably, it also happens if autosizing a row would remove the vertical scrollbar, as well, but I did not confirm that.

You can demonstrate this another way by running your sample and then double-clicking on the bottom edge of each row one at a time from top to bottom. The first 4 rows work fine because even when autosized, they fit within the visible area of the grid. But when you resize row 5, it crosses the bottom edge of the grid which means that the grid now needs a vertical scrollbar and all of the rows are re-initialized to their original height.

So the next question is... why does the grid need to re-initialize the rows in this case. And the answer is because you have set the AutoFitStyle property. Since you are using AutoFitStyle, the existence of a vertical scrollbar changes the width of the columns and when this happens, the grid has to re-initialize certain metrics. I won't go into details on why it needs to do that, because that gets REALLY complicated. :)

Anyway... I don't think there is anything we can do about this. The grid cannot know, in this case, that the metrics should not be re-initalized. It's a sort've catch-22 that it has to adjust the column widths and this causes the row heights to change.

The good news is that there are several very easy things you can do to get around it. The workaround I gave you above works because you are manually setting the height of the row. The row keeps track of this and it knows not to re-initialize itself later on. But that code is something of an ugly hack and you probably don't want it cluttering up your code.

The first and simplest recommendation I have for you is that you set RowSizing on the grid to AutoFree instead of Free. I suspect this is what you really want, anyway, since you are autosizing the rows in code. You probably didn't realize that this setting is better for what you want. Using AutoFree means that when the metrics are re-initialized, the rows are re-autosized and so it all works correctly.

If, for some reason, you must use Free instead of AutoFree, then another way to avoid this issue is to force the vertical scrollbar to display all the time.

Me.gridData.DisplayLayout.Scrollbars = Scrollbars.Vertical

This way, the grid never gets into a case where it has to recalculate the columns widths and to the row heights are not affected.

    Private Sub Resize_Click(sender As System.Object, e As System.EventArgs) Handles Resize.Click, ResizeAgain.Click, ResizeNotes.Click
        For Each rowTemp As UltraGridRow In gridData.Rows.GetFilteredInNonGroupByRows
            rowTemp.PerformAutoSize()
            rowTemp.Height += 1
            rowTemp.Height -= 1
        Next
    End Sub