文件加载挂起时间长| 二进制| C#| 列表

Question

I am wondering why the load time for the file is so long. i would appreciate it if you would take time to look where it says

if (ReadType == 1)

Around 12,000 items loading it takes nearly 12 seconds to load a file with a short structure i don't think this is right. I'm new to c# and could use any pointers attached below is the code and the file structure: here also is attached a video of the issue: video screenshot of file: structureloaded

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace StringEditor
{
 public class ItemStr
  {
    public int a_index;
    public byte[] a_name { get; set; }
    public byte[] a_descr1 { get; set; }
   }
}

private void tsbOpen_Click(object sender, EventArgs e)
    {
        OpenFileDialog ofd = new OpenFileDialog();
        ofd.Filter = "String|*.lod";
        if (ofd.ShowDialog() != DialogResult.OK)
            return;
        if (!ofd.FileName.Contains("strItem") && !ofd.FileName.Contains("strSkill")) //check to see if user isn't opening the right files if not return;
            return;
        else if (ofd.FileName.Contains("strItem"))
            ReadType = 1;
        else if (ofd.FileName.Contains("strSkill"))
            ReadType = 2;


        FileStream fs = new FileStream(ofd.FileName, FileMode.Open);
        BinaryReader br = new BinaryReader(fs);
        if (ReadType == 1)
        {
            int max = br.ReadInt32();
            int max1 = br.ReadInt32();

            for (int i = 0; br.BaseStream.Position < br.BaseStream.Length; i++)
            {
                ItemStr itemstr = new ItemStr();
                itemstr.a_index = br.ReadInt32();
                itemstr.a_name = br.ReadBytes(br.ReadInt32());
                itemstr.a_descr1 = br.ReadBytes(br.ReadInt32());
                itemStringList.Add(itemstr);
                listBox1.Items.Add(itemstr.a_index.ToString() + " - " + Encoding.GetEncoding(ISO).GetString(itemstr.a_name));


            }
            EnableFields();


        }
        fs.Close();
        br.Close();
        if (ReadType == 2)

        {
            int max = br.ReadInt32();
            int max1 = br.ReadInt32();
            for (int i = 0; i < max; i++)
            {
                skillStr skillStr = new skillStr();

                skillStr.a_index = br.ReadInt32();
                skillStr.a_name = br.ReadString();
                skillStr.a_tool_tip = br.ReadString();
                skillStr.a_descr1 = br.ReadString();
                skillStringList.Add(skillStr);
                string test = skillStr.a_index + "- " + skillStr.a_name;
                listBox1.Items.Add(test);


            }
            EnableFields();


        }
        fs.Close();
        br.Close();

    }

Answer 1

I wrote a small test on my core i5 machine. New form, one button, one listbox:

    private void button1_Click(object sender, EventArgs e)
    {
        for (int i = 0; i < 30000; i++)
            listBox1.Items.Add(i.ToString());
    }

(I wrote it guessing at the index numbers in your screenshot). Clicked go. Had to wait 11 seconds before the UI became usable again.

I modified it to this:

    private void button1_Click(object sender, EventArgs e)
    {
        listBox1.BeginUpdate();
        for (int i = 0; i < 30000; i++)
            listBox1.Items.Add(i.ToString());
        listBox1.EndUpdate();
    }

And there was a barely perceptible delay before it was usable again

---

The majority of the problem isn't reading the file, it's having the listbox refresh itself X thousands of times as you add one by one. Use Begin/End update to signal that you're loading a large amount of items...

...but then again, ask yourself what is a user REALLY going to do with X tens of thousands of items in a listbox? As a UI/UX guideline, avoid loading more than about 20 to 30 items into a list. Beyond that it's getting into unnavigable, especially at the quantities you're loading. Consider a type to search box - a one pixel jump of the scroll bar is going to move through more items than can fit vertically in your list!

Answer 2

If you're loading a lot of data from a file (or anywhere) into a list box, consider using the VirtualList approach - an example can be found here:

ListView.VirtualMode Property

You probably also want to consider performing the load in a background thread so that the user doesn't experience the apparent "hanging" delay that loading a lot of data can produce.

Answer 3

Listbox.beginupdate() and listbox.endupdate() fixed my problem thanks for the help guys.