MathNet.Numerics.LinearAlgebra.Double.DenseMatrix.CreateIdentity C# (CSharp) Method

        public static DenseMatrix CreateIdentity(int order)
        {
            return new DenseMatrix(DenseColumnMajorMatrixStorage<double>.OfDiagonalInit(order, order, i => One));
        }

 public void GetMassInverse(MatrixXD massInv)
 {
     massInv.SetSubMatrix(index, index, massInv.SubMatrix(index, 3, index, 3)
                          + 1.0f / Mass * DenseMatrixXD.CreateIdentity(3));
     massInv.SetSubMatrix(index + 3, index + 3, massInv.SubMatrix(index + 3, 3, index + 3, 3)
                          + m_inertiainv);
 }