Earlier today I received the error "An item with the same key has already been added." while attempting to access a GridView that worked perfectly in Telerik v 2008.3 1125. I needed to upgrade to 2009.03 1103 to take advantage of some bug fixes in RadScheduler's RecurrenceRule. So, I had to identify the cause of the error.
After searching around the Telerik site I didn't find an answer. So, after some trial an error, I found the offending code that no longer works:
<telerik:GridHyperLinkColumn
UniqueName="colSampleColumn"
DataNavigateUrlFields="field_one,field_two,field_two"
DataNavigateUrlFormatString="~/foo.aspx?a={0}&b={1}&c={2}"
HeaderText="sample Column"
AllowFiltering="true"
SortExpression="sample_column"
DataType="System.String"
DataTextField="sample_column">
</telerik:GridHyperLinkColumn>
For your benefit I have highlighted the problem. Whereas v 2008.3 1125 did not care if you listed the same column twice, v 2009.03 1103 does.
Here is the correct version:
<telerik:GridHyperLinkColumn
UniqueName="colSampleColumn"
DataNavigateUrlFields="field_one,field_two"
DataNavigateUrlFormatString="~/foo.aspx?a={0}&b={1}&c={1}"
HeaderText="sample Column"
AllowFiltering="true"
SortExpression="sample_column"
DataType="System.String"
DataTextField="sample_column">
</telerik:GridHyperLinkColumn>