Diagonal similarity matrix is a special case and needs its own class. It does not have an actual matrix, instead using a test "if (col == row)" and returning the diagonal value if true, and the off diagonal value if false.

public class DiagonalSimilarityMatrix : SimilarityMatrix

Public Class DiagonalSimilarityMatrix
	Inherits SimilarityMatrix

public ref class DiagonalSimilarityMatrix : public SimilarityMatrix

type DiagonalSimilarityMatrix =  
    class
        inherit SimilarityMatrix
    end