System.Data.DataColumnCollection.CopyTo C# (CSharp) Method

        public void CopyTo(DataColumn[] array, int index)
        {
            if (array == null)
            {
                throw ExceptionBuilder.ArgumentNull(nameof(array));
            }
            if (index < 0)
            {
                throw ExceptionBuilder.ArgumentOutOfRange(nameof(index));
            }
            if (array.Length - index < _list.Count)
            {
                throw ExceptionBuilder.InvalidOffsetLength();
            }

            for (int i = 0; i < _list.Count; ++i)
            {
                array[index + i] = (DataColumn)_list[i];
            }
        }

 public static DataColumn[] GetPrimaryKeyColumns(DataColumnCollection columns)
 {
     var cols = new DataColumn[columns.Count];
     columns.CopyTo(cols, 0);
     return GetColumnsWithExtendedPropertyValue(cols, PrimaryColumnProperty, true, BooleanComparator);
 }