Programmatically adding items to a SharePoint list

using(SPSite site = new SPSite("http://"))
{
using (SPWeb web = site.OpenWeb())
{
SPList list = web.Lists["SharePointList"];
SPListItem Item = list.Items.Add();
item["Title"] = txtCompanyName.Text;
//can add required items
item.Update();
}
}
Note: 1. No need to use SPSecurity.RunWithElevatedPrivileges.
          2. No need to use allowunsafeupdate property
          3. No need to update web object.

Creating a List programmatically using the sharepoint object model

Creating a List programmatically with out of the box List Template Types


You can create a list by picking one of the List Template Types available in the SPListTemplateType object. A full list can be found here.


Guid listId = web.Lists.Add("Test Custom List", "Name of list", SPListTemplateType.GenericList);
SPList list = web.Lists[listId];

OOTB List Templates

Name	BaseType
Events	GenericList
Contacts	GenericList
Tasks	GenericList
PictureLibrary	DocumentLibrary
DiscussionBoard	GenericList
Survey	Survey
DocumentLibrary	DocumentLibrary
Links	GenericList
Document Library	DocumentLibrary
Announcements	GenericList
GenericList	GenericList
WorkflowHistory	GenericList
DataConnectionLibrary	DocumentLibrary
DataSources	DocumentLibrary
GanttTasks	GenericList
CustomGrid	GenericList
NoCodeWorkflows	DocumentLibrary
XMLForm	DocumentLibrary
WebPageLibrary	DocumentLibrary
WorkflowProcess	GenericList
Form Library	DocumentLibrary
wiki	DocumentLibrary
Wiki Page Library	DocumentLibrary
Picture Library	DocumentLibrary
Picture	DocumentLibrary
Contacts	GenericList
Calendar	GenericList
Discussion Board	GenericList
Project Tasks	GenericList
Issue Tracking	Issue
Custom List	GenericList
Custom List in Datasheet View	GenericList
Survey	Survey
Custom Workflow Process	GenericList
Languages and Translators	GenericList
Translation Management Library	DocumentLibrary
DataSources	DocumentLibrary
Data Connection Library	DocumentLibrary
Workflow History	GenericList
No Code Workflows	DocumentLibrary