1:  using System;

   2:  using System.Collections.Generic;

   3:  using System.Text;

   4:  using Microsoft.SharePoint;

   5:   

   6:  namespace ConsoleApplication1

   7:  {

   8:      class Program

   9:      {

  10:          static void Main(string[] args)

  11:          {

  12:              Console.WriteLine("Enter your site URL");

  13:              string strSiteName = Console.ReadLine();

  14:   

  15:              Console.WriteLine("Enter your document library name");

  16:              string strDocumentLibrary = Console.ReadLine();

  17:   

  18:              Console.WriteLine("Enter your group name");

  19:              string strGroup = Console.ReadLine();

  20:   

  21:              Assign(strSiteName, strDocumentLibrary, strGroup);

  22:   

  23:              Console.WriteLine("Done!");

  24:              Console.ReadLine();

  25:          }

  26:   

  27:          public static void Assign(string strSiteName, string strDocumentLibrary, string strGroup)

  28:          {

  29:              SPSite WebApp = new SPSite(strSiteName);

  30:              SPWeb Site = WebApp.OpenWeb();

  31:              SPList list = Site.Lists[strDocumentLibrary];

  32:              SPContentTypeCollection oContentTypes = list.ContentTypes;

  33:              String url = list.RootFolder.ServerRelativeUrl.ToString();

  34:   

  35:              foreach (SPListItem folder in list.Folders)

  36:              {

  37:                  WebApp.AllowUnsafeUpdates = true;

  38:                  Site.AllowUnsafeUpdates = true;

  39:   

  40:                  SPRoleDefinitionCollection roleDefinitions = Site.RoleDefinitions;

  41:                  SPRoleAssignmentCollection roleAssignments = folder.RoleAssignments;

  42:   

  43:                  SPGroup grp = Site.Groups[strGroup];

  44:                  SPRoleAssignment roleAssignment = new SPRoleAssignment(grp);

  45:                  SPRoleDefinitionBindingCollection roleDefBindings = roleAssignment.RoleDefinitionBindings;

  46:   

  47:                  roleDefBindings.Add(roleDefinitions["Contribute"]);

  48:                  roleAssignments.Add(roleAssignment);

  49:   

  50:                  WebApp.AllowUnsafeUpdates = false;

  51:                  Site.AllowUnsafeUpdates = false;

  52:              }

  53:              Site.Close();

  54:              WebApp.Close();

  55:              Site.Dispose();

  56:              WebApp.Dispose();

  57:          }

  58:      }

  59:  }