How to assign permission to the Sharepoint group using CSOM C#

AddPermissionToGroup(clientContext, web, "Group Name", "Read");

public static void AddPermissionToGroup(ClientContext clientContext, Web web, string groupName, string Permission)
{
  try
  {
    using (clientContext)
    {
      //Get group by its name
       var group = clientContext.Web.SiteGroups.GetByName(groupName);
      //Get role by its name
       var roletypes = clientContext.Web.RoleDefinitions.GetByName(Permission);
       clientContext.ExecuteQuery();
       web.BreakRoleInheritance(true, false);
       RoleDefinitionBindingCollection collRoleDefinitionBinding = new       RoleDefinitionBindingCollection(clientContext);
       collRoleDefinitionBinding.Add(roletypes);
       web.RoleAssignments.Add(group, collRoleDefinitionBinding);
       web.Update();
       clientContext.ExecuteQuery();
    }
  }
  catch (Exception ex)
  {
     ErrorLogger.LogException(ex);
  }
}