C# 创建字段数组

Question

嘿！ 我想创建一个字段数组。但是我的代码返回以下错误：字段“WindowsFormsApplication1.Form1.fieldArray”从未分配给，并且始终具有其默认值 null。

对如何解决此错误有何建议？

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;

namespace WindowsFormsApplication1
{
    public partial class Form1 : Form
    {
        private Field[] fieldArray;
        private Field f; 
        public Form1()
        {
            InitializeComponent();
        }

        private void populateTree(string path, TreeNode tv1)
        {
            string[] dir = Directory.GetDirectories(path);
            foreach (string d in dir)
            {
                string entry = Path.GetFileName(d);
                TreeNode t = tv1.Nodes.Add("Folder", entry, 0);
                populateTree(d, t);
            }
            string[] files = Directory.GetFiles(path);
            foreach (string f in files)
            {
                string entry = Path.GetFileName(f);
                tv1.Nodes.Add(f, entry, 1);
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //populate the tree
            TreeNode t = treeView1.Nodes.Add("Units");
            populateTree(@"..\units\", t);

            f = new Field();

            for (int i = 0; i < 10; i++)
            {
                fieldArray[i] = new Field();
            }

            fieldArray[1].label.AutoSize = true;
            fieldArray[1].label.Location = new System.Drawing.Point(323, 9);
            fieldArray[1].label.Name = "Programtittle";
            fieldArray[1].label.Text = "UAI UnitDef Editor";
            this.Controls.Add(fieldArray[1].label);

            int clabel = 36;
            //fieldArray[1].varName = new string[] { "unitName", "name", "description" }; //define labels

            //popluate label
            for (int i = 1; i < fieldArray[i].varName.Length; i++)
            {
                fieldArray[i].label = new Label();
                fieldArray[i].label.AutoSize = true;
                fieldArray[i].label.Location = new System.Drawing.Point(323, clabel);
                fieldArray[i].label.Name = "label";
                this.Controls.Add(fieldArray[i].label);
                fieldArray[i].label.Text = fieldArray[i].varName[i];
                clabel = clabel + 26;
            }

            //populate textbox 
            int cbox = 33;
            for (int i = 0; i < fieldArray[i].varName.Length; i++) 
            {

                fieldArray[i].txtBox = new TextBox();
                fieldArray[i].txtBox.Location = new System.Drawing.Point(380, cbox);
                fieldArray[i].txtBox.Name = "txtBox";
                fieldArray[i].txtBox.Size = new System.Drawing.Size(100, 50);
                this.Controls.Add(fieldArray[i].txtBox);

                cbox = cbox + 26;
            }
        }

        private void populateLabelTxtBox(string path)
        {
            //f.txtBox.Multiline = true; //added for testing purpose; 

            //read,split file 
            string text = System.IO.File.ReadAllText(path);

            char[] delimiters = new char[] { '{', '=', ';', '}' };
            string[] parts = text.Split(delimiters, StringSplitOptions.RemoveEmptyEntries);

            for (int i = 0; i < parts.Length; i++)
            {
                fieldArray[i].txtBox.Text = parts[i];
            }
        }

        private void treeView1_NodeMouseDoubleClick(object sender, TreeNodeMouseClickEventArgs e)
        {
            if (treeView1.SelectedNode.Name != "Folder")
            {
                string text = System.IO.File.ReadAllText(treeView1.SelectedNode.Name);
                //f.txtBox.Text = text;
                populateLabelTxtBox(treeView1.SelectedNode.Name);
            }
        }
    }
}

Answer 1

列表可能比数组更容易，但是：您将项目分配给空数组；一旦你知道你需要的数字，首先创建数组：

fieldArray = new Field[10];       
for (int i = 0; i < 10; i++)
{...}

但是，我个人会使用一个列表：

private readonly List<Field> fields = new List<Field>();
...
fields.Add(someField);

Answer 2

你永远不会将 fieldArray 初始化

//Change
private Field[] fieldArray;

为

private Field[] fieldArray = new Field[10];

Answer 3

您从未初始化过fieldArray。表单构造函数中类似 fieldArray = new Field[10]; 的内容应该可以做到这一点。

Answer 4

在尝试访问 fieldArray 中的元素之前，您必须像这样初始化数组：

fieldArray = new Field[/*size of the array*/];

但是，请小心创建一个足够大的数组来存储所有字段。假设您创建一个包含 5 个元素的 Field[5] 数组，并且尝试为 fieldArray[5] 赋值，您将收到 OutOfBounds 异常。

Answer 5

在执行初始化数组每个元素的循环之前，您需要初始化数组本身：

fieldArray = new Field[10]; // Create this with the appropriate size
for (int i = 0; i < 10; i++)
{
    fieldArray[i] = new Field();
}

另一方面，您实际上从未设置 fieldArray[0] - 我怀疑您的代码是显式设置 fieldArray[1].XXX 应该适用于元素 0。

Answer 6

声明数组时初始化它：

private Field[] fieldArray = new Field[100]; // size == 100

Answer 7

我没有看到任何分配数组的行：就像

int number_of_elements = 100;
fieldArray = new Field[number_of_elements];

如果字段数量是动态的，我会使用 ArrayList，例如

List fieldArray = new List();

然后向其中添加元素：

fieldArray.Add(...)

Answer 8

您必须初始化您的数组

fieldArray = new Field[10];

Answer 9

fieldArray[i] = new Field();

上面的代码让你认为数组已经初始化，但实际上它还没有。您需要像下面这样的东西来为数组分配一些内存。

fieldArray = new Field[/*length or size*/];