Role Assignments For the Site

SPRoleAssignmentCollection webRoleAssignments =
web.RoleAssignments;

Response.Write("All role assignments in this site: " + "
");

foreach (SPRoleAssignment webRoleAssignment in webRoleAssignments)
{
Response.Write(webRoleAssignment.Member.Name + " "
+ webRoleAssignment.RoleDefinitionBindings[0].Name + " "
+ webRoleAssignment.Parent.ToString() + "
");
}

Role Definitions

// Role definitions are represented as "Permissions Levels"
// in user interface
SPRoleDefinitionCollection roleDefinitions = web.RoleDefinitions;
Response.Write("All role definitions in this site: " + "
");
foreach (SPRoleDefinition roleDefinition in roleDefinitions)
{
Response.Write(roleDefinition.Name + "
");
}

SharePoint Group Users

// All users in "Students" SharePoint group
users = web.Groups["Students"].Users;

Response.Write("All users in \"Students\" SharePoint group: " + "
");
foreach (SPUser user in users)
{
Response.Write(user.Name + "
");
}