Why Export to excel code in vb.net not working on Server ,when its working on local machine.?

You're attempting to open the Excel file on the server. When you run the site locally, that works, since the client and server are the same computer. When you deploy the site to a real server, it's not going to work. You need to send the Excel file to the client using Response.TransmitFile.

Also, based on your comment, you're trying to write the file to the root of the C: drive. Since your site won't be running as an administrative user, it won't have permission to write to that location. Pick a folder to which it does have access - for example, the App_Data folder within the site.

DataSet ds = CreateSampleData();

// Build a path to which the application can write.
// Use a random file-name to avoid collisions from multiple simultaneous requests.
string targetFolder = Server.MapPath("~/App_Data/");
string excelFilename = Path.GetRandomFileName() + ".xlsx";
string excelPath = Path.Combine(targetFolder, excelFilename);

// Create the Excel file:
CreateExcelFile.CreateExcelDocument(ds, excelPath);

// Transmit the file to the client:
Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
Response.AddHeader("Content-Disposition", "attachment;filename=Sample.xlsx");
Response.TransmitFile(excelPath);
Response.Flush();

// Delete the temporary file:
File.Delete(excelPath);