Selecting a part of string in input field

InputField.SelectAll() can select all text in a input field of UGUI, but what with I only want to select a part of the string? E.g.:

inputField.Select(6,5); // Select length of 5 from index 6, just like string.SubString(6,5)

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Is that possible?!? I cannot find any solution.

Check InputField.selectionAnchorPosition and InputField.selectionFocusPosition.