Entering data into SharePoint lists via Silverlight forms

There shouldnt be any problem using CSOM (.NET client API reference for SharePoint 2013)

Example code:

// Starting with ClientContext, the constructor requires a URL to the // server running SharePoint. ClientContext context = new ClientContext("http://SiteUrl"); // Assume that the web has a list named "Announcements". List announcementsList = context.Web.Lists.GetByTitle("Announcements"); // We are just creating a regular list item, so we don't need to // set any properties. If we wanted to create a new folder, for // example, we would have to set properties such as // UnderlyingObjectType to FileSystemObjectType.Folder. ListItemCreationInformation itemCreateInfo = new ListItemCreationInformation(); ListItem newItem = announcementsList.Items.Add(itemCreateInfo); newItem["Title"] = "My New Item!"; newItem["Body"] = "Hello World!"; newItem.Update(); context.ExecuteQuery(); 

More info could be found here: http://msdn.microsoft.com/en-us/library/fp179912.aspx