sqlmathnetexample.cs

using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
using System.Linq;
using System.Numerics;
using System.Runtime.InteropServices;
using System.Collections.Generic;
using MathNet.Numerics.LinearAlgebra;
using MathNet.Numerics.LinearAlgebra.Double;

public partial class UserDefinedFunctions
{
    [Microsoft.SqlServer.Server.SqlFunction]
    public static SqlDouble[][] MatrixKernel(SqlDouble[,] param)
    {
        Double[][] val = Array.ConvertAll(param.ToJaggedArray(),
            el => Array.ConvertAll<SqlDouble, Double>(el, x => x.Value));
        Matrix A = DenseMatrix.OfArray(CreateRectangularArray<Double>(val));
        Vector<double>[] nullspace = A.Kernel();
        return nullspace.Select(i => i.Select(j => new SqlDouble(j)).ToArray()).ToArray();
    }

    static T[,] CreateRectangularArray<T>(T[][] arrays)
    {
        
        int minorLength = arrays[0].Length;
        T[,] ret = new T[arrays.Length, minorLength];
        for (int i = 0; i < arrays.Length; i++)
        {
            var array = arrays[i];
            if (array.Length != minorLength)
            {
                throw new ArgumentException
                    ("All arrays must be the same length");
            }
            for (int j = 0; j < minorLength; j++)
            {
                ret[i, j] = array[j];
            }
        }
        return ret;
    }
}
internal static class ExtensionMethods
{
    internal static T[][] ToJaggedArray<T>(this T[,] twoDimensionalArray)
    {
        int rowsFirstIndex = twoDimensionalArray.GetLowerBound(0);
        int rowsLastIndex = twoDimensionalArray.GetUpperBound(0);
        int numberOfRows = rowsLastIndex + 1;

        int columnsFirstIndex = twoDimensionalArray.GetLowerBound(1);
        int columnsLastIndex = twoDimensionalArray.GetUpperBound(1);
        int numberOfColumns = columnsLastIndex + 1;

        T[][] jaggedArray = new T[numberOfRows][];
        for (int i = rowsFirstIndex; i <= rowsLastIndex; i++)
        {
            jaggedArray[i] = new T[numberOfColumns];

            for (int j = columnsFirstIndex; j <= columnsLastIndex; j++)
            {
                jaggedArray[i][j] = twoDimensionalArray[i, j];
            }
        }
        return jaggedArray;
    }
}