How to pass multiple querysting parameters in the Hyperlink column (Datagrid control)

<asp:hyperlinkcolumn DataNavigateURLField="field_id" DataNavigateURLFormatString="/details.aspx?id={0}" >

I want "details.aspx?id=filed_id&mykey=key_field"

how to pass mykey as querysting parameter?

Sadly, you can't. However, you can use a template column and create a hyperlink within it that can contain any number of querystring arguments.