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Silverlight Issues

Silverlight often feels a bit much like a work in progress, other times just like parts weren’t thought through all the way.  I thought I’d post a few examples of the sorts of things we’ve run into while developing with it.  Main lesson is, somehow you will need to plan for the unplanned.

For example, in the global application error handler:

Exception tmp = e.ExceptionObject;
if (tmp != null)
    while (tmp.InnerException != null)
        tmp = tmp.InnerException;

    // Silverlight defect where File stream can error out if file open failed due 
    // to an open file error, then later the garbage collector tries to clean up
    // the stream.  Can't be reliably handled at regular code level because we don't
    // get back a stream to operate on due to the file method erroring out.
    if (tmp is InvalidOperationException)
        // string parse is bad and fragile, but I can't find any way to get the error code
        // this should be error code -2146233079 per Reflector, but, well.
        if (tmp.Message.Contains("UI Thread") && tmp.Message.Contains("System.Windows.SaveFileStream.Dispose"))
            // ignore
. . .

Forums suggest this one may have been fixed in 4.

My favorite issue is a layout issue: If you want a label next to a textbox, you put it in a horizontal stackpanel.  But horizontal stackpanels don’t constrain themselves horizontally.  Bottom line?  Your labels won’t wrap and will clip instead.   Solution?  Specify fixed widths on your labels.  I wonder if nobody did a form with labels next to textboxes and a dynamic layout all during the testing and design phase.

We also have these gems:

                // NOTE: A "Dialogs must be user initiated" error can crop up if running under the debugger.
                // It is a spurious error and will not happen when not using the debugger.
                // See


// firefox doesn't render our silverlight right in an iframe.
function isfirefox() {
    if (/Firefox[\/\s](\d+\.\d+)/.test(navigator.userAgent)) {
        return true;
    } else {
        return false;


    This service has to be activated using basicHttp because Silverlight cannot 
    function against wsHttp.  


        //sizechanged doesn't fire properly when column widths are changed, tabs need to
        // be hidden and refreshed for it to update... also, this can be fired
        // too early, before the column width has really changed. Layoutupdated seems to mostly work, though.


// assigning width directly is sub-optimal because
// it won't handle a situation where this column should be bigger
// than the main column... but the grid doesn't redraw properly
// if we don't.  Tried forcing just minwidth to work 
// with invalidatemeasure, invalidatearrange,
// measure, arrange, and updatelayout, all of which redraw the column
// header right but not the column data.

Categories: ASP.NET | Silverlight
Posted by David Eison on Sunday, September 26, 2010 5:59 PM
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