It doesn't sound to me like you really do want to customize the save dialogue. The reason I'm saying this is because you say:
shubham pateriya wrote:in this dialog box there is 'Save As Type' dropdown, I need to customize this dropdown and I want to show '.xls' and '.xlsx' extention type in this dropdown, and when user chooses any of extention type , file saves in that formate.
Changing the file extension
won't change the file format, if you want the file to be in a certain format you have to generate in that format on the server. All of the things you want to do happen on the server side, not at the client, by the time things have gotten to the save as dialogue on the client it's too late to be doing them.
If you want to force a file download, set the
content-disposition header on the server side and ensure you've set an appropriate
MIME type for the format of the file you've generated.