Hopefully we’ll see a new build of Blend 2.5 very soon as I’m quite tired of not being able to size DataGrid columns properly. In the meantime I’ve resorted to using the MinWidth property, but it isn’t quite the same.
If you are busy trying to develop using Microsoft Silverlight 2 beta 2 and Microsoft Expression Blend 2.5 June Preview you might have encountered errors while working in Blend such as The TypeConverter for "DataGridLength" does not support converting from a string. although Visual Studio doesn’t complain about the XAML and the code runs just fine.
Well its a confirmed issue in Expression Blend according to the feedback I’ve received on my bug report. The official word from Microsoft is as follows:
Thank you for your feedback. For the June Preview Blend does not support type converters from managed code (all the type converters defined in non-runtime assemblies). This is something that we are working on supporting for RTM but unfortunately do not have it working yet.
What this means is that any custom control development, including Microsoft’s own controls can potentially suffer from this issue as TypeConverter implementations that are not part of the Silverlight 2 beta 2 runtime are not supported. If you have encountered this issue in Expression Blend then please rate and validate the bug so it will be fixed.