WebGrid has OnExport server-side event that occurs when exporting data from WebGrid is performed. The event handler receives an argument of type ExportEventArgs containing data related to this event One of the ExportEventArgs property is the “Table” property.

The “Table” property gets or sets the structure of table used by the event. We can utilize this property so that only checked rows that are going to be exported.

The snippet code below shows how to implement such scenario on a simple single-level WebGrid.

protected void WebGrid1_Export(object sender, ISNet.WebUI.WebGrid.ExportEventArgs e)
{
    // get the total rows in the root table of WebGrid
    int totalRows = WebGrid1.RootTable.Rows.Count;        

    for (int i = 0; i < totalRows; i++)
    {
        // get the number of checked rows
        int checkedRowsCount = WebGrid1.RootTable.GetCheckedRows().Count;
            
        // a flag that shows whether row is match to one of the rows in the checked rows
        bool IsMatch = false;

        foreach (string keyValue in WebGrid1.RootTable.GetCheckedRows())
        {
            // if current row is equal to one of the rows in the checked rows
            // then break
            if (e.Table.Rows[i].KeyValue.ToString() == keyValue)
            {
                IsMatch = true;
                break;
            }
        }

        // if current row is equal to one of the rows in the checked rows
        // then passes to the next iteration
        // else remove current row
        if (IsMatch)
            continue;            
        else
        {
            e.Table.Rows.RemoveAt(i);
            i--;
            totalRows--;
        }
    }

    // set the "IsRowChecker" to be not visible during export
    e.Table.Columns.GetNamedItem("IsRowChecker").Visible = false;
}

A simple sample is enclosed as attachment. Please have the sample tested on your end and kindly let us know whether it helps or not.