Searching with search dialog can be enabled by setting the ToolBarSettings.ShowSearchButton to true. This will enable the search dialog button (bottom left on the screenshot), which will in turn launch the search dialog. Toenable multiple search filters in the dialog, set the SearchDialogSettings.MultipleSearch to true as well.

<trirand:JQGrid runat="server" ID="JQGrid1" DataSourceID="SqlDataSource1">
    <ToolBarSettings ShowSearchButton="true" />
    <SearchDialogSettings MultipleSearch="true" />
</trirand:JQGrid>

jqGrid for ASP.NET will by default automatically evaluate filtering against the datasource and filter row data. It will also fire the Searching (before) and Searched (events). They will be fired for each distinct filter (e.g. in the case above, 3 times - one for each filter). The Searching event can be cancelled (set eventArgs.Cancel to true) and you can implement custom filtering expressions per your requirements.

You can control the various display options of the search dialog by using properties in the SearchDialogSettings collection, e.g.

<SearchDialogSettings 
    Height="200" 
    Width="200" 
    Draggable="false" 
    FindButtonText="Find" 
    ResetButtonText="Reset"
    LeftOffset="100"
    TopOffset="100"
    Modal="true"
    MultipleSearch="true"
 />