帮我看看错误哈

Question

错误在最后一行，
索引或主关键字不能包含一个 空 (Null) 值。
怎么会这样呢picDataSet的DataTablePic只有两个元素啊
为什么会这样呢？
        private void Form1_Load(object sender, EventArgs e)
        {
            this.picTableAdapter.Fill(this.picDataSet.Pic);            dataGridView1.DataSource = picDataSet.Pic;
        }        private void button1_Click(object sender, EventArgs e)
        {
            openFileDialog1.FileName = "";
            openFileDialog1.InitialDirectory = "e:\\zzz";
            openFileDialog1.Filter = "pic(*.jpg)|*.jpg";            if (openFileDialog1.ShowDialog() == DialogResult.OK)
            {
                this.pictureBox1.Image = new Bitmap(openFileDialog1.FileName);                FileStream fileStream = new FileStream(openFileDialog1.FileName, FileMode.Open, FileAccess.Read);
                BinaryReader binaryReader = new BinaryReader(fileStream);                byte[] imgBytes;
                imgBytes = binaryReader.ReadBytes((int)fileStream.Length);                DataRow row = picDataSet.Pic.NewRow();                row["ID"] = 5;
                row["PICTURE"] = imgBytes;                picDataSet.Pic.Rows.Add(row);                this.picTableAdapter.Update(this.picDataSet.Pic);//错误出现的地方            }