Below is the simple code to make you understand how to fetch Top 100 records. This is actually an idea to make it clear how you can do to fetch Top 100 rows.
private DataTable GetDatasource()
{
DataTable dtable = new DataTable();
string _Query = string.Empty;
_Query = "SELECT TOP 100 * FROM Customers";
return dtable;
}
protected void btnRadioButton1_Click(object sender, EventArgs e)
{
DataTable dtable = GetDatasource();
GridViewExportUtil.Export("Customers.xls", dtable);
}
Hope it helps.