C＃将值输入到多维数组

Question

我用c＃构建一个程序，并在其上包含了dataGridView。我对dataGridView数据进行数学运算，然后将结果插入到多维数组中。但我收到错误消息，说“对象引用未设置为对象的实例”。

这里是我的代码：

1. frm_clustering.cs

   public void hitungMatriksJarak()
   {
       clusteringModel cm = new clusteringModel();
   
       int i = 0;
       int j = 0;
       for (i = 0; i < this.dgv_clustering.Rows.Count; i++)
       {
           for (j = 0; j < this.dgv_clustering.Rows.Count; j++)
           {
               cm.matriks[j,i] = Math.Sqrt(Math.Pow(Convert.ToDouble(this.dgv_clustering[1, i].Value), 2) +
                                            Math.Pow(Convert.ToDouble(this.dgv_clustering[2, i].Value), 2) +
                                            Math.Pow(Convert.ToDouble(this.dgv_clustering[3, i].Value), 2) +
                                            Math.Pow(Convert.ToDouble(this.dgv_clustering[4, i].Value), 2));
           }
       }
   }
   

2. clusteringModel.cs：

   class clusteringModel
   {
       private int _jmlKel;
       public int jmlKel
       {
           get { return _jmlKel; }
           set { _jmlKel = value; }
       }
   
       private double[,] _matriks = new double[500,500];
       public double[,] matriks
       {
           get { return _matriks; }
           set { _matriks = value; }
       }
   }