code gives you SPFieldLookupValueCollection in array format

SPFieldLookupValueCollection fieldValues1 = new SPFieldLookupValueCollection();

foreach (Control ctrl in PnlProfileTags.Controls)// Form Control Id

{

    CheckBox cb = ctrl as CheckBox;

    if (cb != null)

    {

        if (cb.Checked)

        {

            int TageID = Convert.ToInt32(cb.ID.Substring(4));

 var TagItm = web.Lists[listTags.Title].GetItemById(TageID);

 fieldValues1.Add(new SPFieldLookupValue(TagItm.ID, TagItm.Title));

         }

     }

 }

List<string> strValues = new List<string>();

 foreach (var item in fieldValues1)

 {

     strValues.Add(item.ToString().Split('#')[1]);

 }

 string[] ProfiletagformValue = strValues.ToArray();// output 0 SharePoint

                                                              1 Dotnet

                                                              2 Hr