Hi Saravana,
Thank you for your interest in Syncfusion products.
I am afraid that I was not able to reproduce the issue. I have created a simple sample with your code snippet and test this issue. Here exporting the grid to excel works fine.
Please refer the sample in the below link:
http://websamples.syncfusion.com/samples/Grid.Web/6.2.0.40/73511/ExportGridtoExcel.ZipPlease have a look at the above sample and if still the issue exists, could you please try reproducing it in the above sample and send us the modified sample so that we could sort out the cause of the issue
and provide you a solution?
Regards,
G.Yavana