How to boost a document during indexing about examine HOT 2 OPEN

/// <summary>
/// Returns the field's index-time boost.
/// <para/>
/// Only fields can have an index-time boost, if you want to simulate
/// a "document boost", then you must pre-multiply it across all the
/// relevant fields yourself.
/// <para/>
/// The boost is used to compute the norm factor for the field.  By
/// default, in the <see cref="Search.Similarities.Similarity.ComputeNorm(FieldInvertState)"/> method,
/// the boost value is multiplied by the length normalization factor and then
/// rounded by <see cref="Search.Similarities.DefaultSimilarity.EncodeNormValue(float)"/> before it is stored in the
/// index.  One should attempt to ensure that this product does not overflow
/// the range of that encoding.
/// <para/>
/// It is illegal to return a boost other than 1.0f for a field that is not
/// indexed (<see cref="IIndexableFieldType.IsIndexed"/> is false) or omits normalization values
/// (<see cref="IIndexableFieldType.OmitNorms"/> returns true).
/// </summary>
/// <seealso cref="Search.Similarities.Similarity.ComputeNorm(FieldInvertState)"/>
/// <seealso cref="Search.Similarities.DefaultSimilarity.EncodeNormValue(float)"/>
float Boost { get; }

  var titleField = e.Document.GetField("title") as TextField;
  if (titleField != null)
           titleField.Boost = boostValue;