How to select item of treelist in sitecore programmatically

I have a office location treelist in a content item, programmatically I have to select a location. How to do it... any information

The way we set a text value to a sitecore field programatically similarly it is for multilist or treelist any field. Only difference is in treelist and multilist content ids are pipeline separated e.g. {GUID for office location 1}|{GUID for office location 2}

So you need to edit the treelist field like below:

using (new Sitecore.SecurityModel.SecurityDisabler())
{

  Item item = master.GetItem("path of your item");
  if (item !=null)
  {
    item.Editing.BeginEdit();
    item["Office Location Treelist fieldname"] = "{40764AF5-F3C9-4B36-8B51-3EF36702E3DB}|{406200EB-E5D5- 
                                47FB-9031-8A49A7C8FC06}";   
                 // Make sure these item ids belong to datasource of your treelist
    item .Editing.EndEdit();
  }