реобразовать приведенный ниже массив fieldList в словарь какDictionary<string,column> (i.e. Dictionary of name property of column class as key and value property of dictionary as column object).

public class columninfo
{
 public string name {get;set;}
 public column[] fieldList {get;set;}
}

public class column
{
  public string name {get;set;}
  public string fieldname {get;set}
  public string format {get;set;}
}