Columnidx should be either 0 (first column), 1 (2nd column), 2, 3 etc.
Your ListView control in your XML file should also follow a similar format;
code:
<Control xsi:type="ListViewControl" Id="lstContacts">
<Position Top="20" Width="326" Left="12" Height="162"></Position>
<Attributes>
<AlwaysShowSelection>false</AlwaysShowSelection>
</Attributes>
<ReportView>
<SortColHeader>true</SortColHeader>
<HasCheckboxes>true</HasCheckboxes>
</ReportView>
<Columns>
<Column>
<ColumnId>colEmail</ColumnId>
<Label>Email</Label>
<Width>30</Width>
</Column>
<Column>
<ColumnId>colName</ColumnId>
<Label>Nickname</Label>
<Width>71</Width>
</Column>
</Columns>
</Control>
In this example colEmail would be the first column (ie. columnidx = 0) and colName would be the 2nd column (ie. columnidx = 1)
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