Create a New SharePoint Permission Level and Bind it to an Existing SharePoint Group

 这个例子是新建一个  permission level,名字为Example_xxxxxxxxxxx.建好之后.绑定这个permission level 到一个已经存在的组名字为Foo.

using (SPSite site = new SPSite( "http://moss/sites/PermExample" ))
{
   using (SPWeb rootWeb = site.RootWeb)
   {
       string permissionLevelName = "Example_"+System.DateTime.Now.Ticks.ToString();

        // Create a new Permission Level
        SPRoleDefinition newPermissionLevel = new SPRoleDefinition();
        newPermissionLevel.Name = permissionLevelName;
        newPermissionLevel.Description = "Example Permission Level";
        newPermissionLevel.BasePermissions =
                SPBasePermissions.AddListItems |
                SPBasePermissions.BrowseDirectories |
                SPBasePermissions.EditListItems |
                SPBasePermissions.DeleteListItems |
                SPBasePermissions.AddDelPrivateWebParts;

        // Add the permission level to web
        rootWeb.RoleDefinitions.Add(newPermissionLevel);

        // Bind to the permission level we just added
        newPermissionLevel = rootWeb.RoleDefinitions[permissionLevelName];

        // Create a new role Assignment using the SharePoint Group "Foo"
        SPRoleAssignment roleAssignment = new SPRoleAssignment( (SPPrincipal)rootWeb.SiteGroups[ "Foo" ] );

        // Add the Permission Level to the Foo SharePoint Group
        roleAssignment.RoleDefinitionBindings.Add(newPermissionLevel);

        // Add the new Role Assignment to the web
        rootWeb.RoleAssignments.Add(roleAssignment);

        rootWeb.Close();
   }
   site.Close();
}
这样就新建成功了.也绑定到了已经存在的组.!

Create a permission level

If there is no permission level similar to the one you need, you can create one and include just the permissions that you need.
1:On the Site Settings page, under Users and Permissions, click Advanced permissions.
2:On the toolbar, click Settings, and then click Permission Levels.
3:On the toolbar, click Add a Permission Level.
4:On the Add a Permission Level page, in the Name box, type a name for the new permission level..
5:In the Description box, type a description for the new permission level..
6:In the list of permissions, select the check boxes to add permissions to the permission level
7:Click Create.