The SPWebApplication objects represents a SharePoint Web Application, which essentially is an IIS virtual server. Using this class we can do some high level operations. Please find some of the actions you can perform.

·         Create a web application

·         Collect all the features in a particular web application

·         Delete a web application

·         Some administrative task for the web application.

Below is a small example to delete a web application

SPWebApplication MyWebApplication = SPWebApplication.Lookup(new Uri("URL Web application URL "));

MyWebApplication.Delete

You can also use SpWebApplication to set the maximum file size or per-user alert settings for a web application

MyWebApplication.MaximumFileSize = 50;

MyWebApplication.AlertsMaximum = 500;

MyWebApplication.Update();