Question

当我在string[] values = lineuser.Split(' ');编译代码时，我得到“对象引用没有设置为对象的实例”错误。有什么想法吗？

namespace function
{
    public partial class Form1 : Form
    {

            float userscore,itemscore,result;
            string lineitem, lineuser;
            //float[][] a = new float[89395][100];
            //float[][] b = new float[1143600][100];
            float[][] a = Enumerable.Range(0, 89395).Select(i => new float[100]).ToArray();
            float[][] b = Enumerable.Range(0, 1143600).Select(j => new float[100]).ToArray();
            //float[,] c = new float[89395, 100];
            StreamReader fileitem = new StreamReader("c:\\ITEM_SVD_FULL.txt");
            StreamReader fileuser = new StreamReader("c:\\USER_SVD_FULL.txt");
        public Form1()
        {
            InitializeComponent();

             for (int x = 0; x <= 8939500; x++)
            {
                lineuser = fileuser.ReadLine();
                string[] values = lineuser.Split(' '); //<------the line's error
                int userid, factoriduser;
                foreach (string value in values)
                {
                    userid = Convert.ToInt32(values[0]);
                    factoriduser = Convert.ToInt32(values[1]);
                    userscore = Convert.ToSingle(values[2]);
                    a[userid][factoriduser] = userscore;
                }
            }

            for (int y = 0; y <= 114360000; y++)
            {
                lineitem = fileitem.ReadLine();
                string[] valuesi = lineitem.Split(' ');
                int itemid, factoriditem;
                foreach (string value in valuesi)
                {
                    itemid = Convert.ToInt32(valuesi[0]);
                    factoriditem = Convert.ToInt32(valuesi[1]);
                    itemscore = Convert.ToSingle(valuesi[2]);
                    b[itemid][factoriditem] = itemscore;
                }

            }

        }
        public float dotproduct(int userid,int itemid)
        {

            //get the score of 100 from user and item to dotproduct
            float[] u_f = a[userid];
            float[] i_f = b[itemid];

            for (int i = 0; i <u_f.GetLength(1); i++)
            {
                result += u_f[userid] * i_f[itemid];
            }
            return result;

        }

        private void btn_recomm_Click(object sender, EventArgs e)
        {
            if(txtbx_id.Text==null)
            {
                MessageBox.Show("please insert user id");
            }
         if (txtbx_id.Text != null && txtbx_itemid==null)
          {
           int sc = Convert.ToInt32(txtbx_id.Text);
           if (sc>=0 &&sc<=89395)
            {
              for (int z=0;z<=1143600;z++)
                {
                  dotproduct(sc,z);
                }
               //Hashtable hashtable = new Hashtable();
               //put the result in hashtable
               //foreach (DictionaryEntry entry in hashtable)
                 //{
                   //Console.WriteLine("{0}, {1}", entry.Key, entry.Value);
                // }
            }
         }
            if (txtbx_id!=null &&txtbx_itemid!=null)
            {
                int uid = Convert.ToInt32(txtbx_id.Text);
                int iid = Convert.ToInt32(txtbx_itemid.Text);
                {
                    if (uid>=0 && uid<=89395 && iid>=0 && iid<=1143600)
                    {
                        dotproduct(uid,iid);
                        MessageBox.Show("The Score of user id "+uid+" is "+result);
                    }
                }

Answer 1

请检查lineuser变量null

    public Form1()
    {
        InitializeComponent();

         for (int x = 0; x <= 8939500; x++)
         {
            if(!string.IsNullorEmpty(lineuser) //<--- check the string is empty
            {   
                string[] values = lineuser.Split(' '); //<------the line's error
                int userid, factoriduser;
                foreach (string value in values)
                {
                  userid = Convert.ToInt32(values[0]);
                  factoriduser = Convert.ToInt32(values[1]);
                  userscore = Convert.ToSingle(values[2]);
                  a[userid][factoriduser] = userscore;
                }
            }
         }

         for (int y = 0; y <= 114360000; y++)
         {

            lineitem = fileitem.ReadLine();

            if(!string.IsNullorEmpty(lineitem) //<--- check the string is empty
            {

               string[] valuesi = lineitem.Split(' ');
               int itemid, factoriditem;
               foreach (string value in valuesi)
               {
                 itemid = Convert.ToInt32(valuesi[0]);
                 factoriditem = Convert.ToInt32(valuesi[1]);
                 itemscore = Convert.ToSingle(valuesi[2]);
                 b[itemid][factoriditem] = itemscore;
               }
            }
        }

    }

现在您可以避免错误。

Answer 2

您尚未打开Stream fileuser，因此它仍然为空。

Answer 3

在您的班级中定义全局变量时打开文件确实是一种不好的做法但是作为其中的一部分，当你调用ReadLine时，结果可能是null，因为没有更多的行可以读取，你也不会检查这种情况。

查看上面显示的代码，不需要为文件流提供全局变量，因此，两个文件都应遵循处理资源时常用的模式（OPEN / USE / CLOSE）

    public Form1()
    {
        InitializeComponent();

        string lineuser;

        // OPEN
        using(StreamReader fileuser = new StreamReader("c:\\USER_SVD_FULL.txt"))
        {
            // USE
            while((lineuser = fileuser.ReadLine()) != null)
            {
                 string[] values = lineuser.Split(' ');
                 ....
            }
        } //CLOSE & DISPOSE
        ....

        string lineitem;
        using(StreamReader fileitem = new StreamReader("c:\\ITEM_SVD_FULL.txt"))
        {
            while((lineitem = fileitem.ReadLine()) != null)
            {
                string[] valuesi = lineitem.Split(' ');
                ....
            }
        }

“编译期间未将对象引用设置为对象的实例”错误

3 个答案: