Question

我想用C＃中的winforms绘制一些东西。我在网上发现了一段代码，让我开始，我已经包含在下面。我试图理解这些winforms是如何工作的，我想知道的一件事是Form1_Load方法中的部分，它说的是

chart = new Graph.Chart();

变量chart已在类的开头初始化，但我想为什么不将它移到上面的命令之上。但这不起作用，但我不明白为什么。

当我尝试移动它时，它给了我这个错误：“错误1'plotting.Form1'不包含'chart'的定义，也没有扩展方法'chart'接受类型'的第一个参数plotting.Form1'可以找到（你错过了使用指令或汇编引用吗？）“

using System;
using System.Drawing;
using System.Windows.Forms;
using Graph = System.Windows.Forms.DataVisualization.Charting;

namespace plotting
{
public partial class Form1 : Form
{
    Graph.Chart chart; //CAN I MOVE THIS TO (***)?
    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        const int MaxX = 20;
        // Create new Graph
        //(***) DOESN*T WORK, IF I MOVE IT HERE
        chart = new Graph.Chart();
        chart.Location = new System.Drawing.Point(10, 10);
        chart.Size = new System.Drawing.Size(700, 700);
        // Add a chartarea called "draw", add axes to it and color the area black
        chart.ChartAreas.Add("draw");
        chart.ChartAreas["draw"].AxisX.Minimum = 0;
        chart.ChartAreas["draw"].AxisX.Maximum = MaxX;
        chart.ChartAreas["draw"].AxisX.Interval = 1;
        chart.ChartAreas["draw"].AxisX.MajorGrid.LineColor = Color.White;
        chart.ChartAreas["draw"].AxisX.MajorGrid.LineDashStyle = Graph.ChartDashStyle.Dash;
        chart.ChartAreas["draw"].AxisY.Minimum = -0.4;
        chart.ChartAreas["draw"].AxisY.Maximum = 1;
        chart.ChartAreas["draw"].AxisY.Interval = 0.2;
        chart.ChartAreas["draw"].AxisY.MajorGrid.LineColor = Color.White;
        chart.ChartAreas["draw"].AxisY.MajorGrid.LineDashStyle = Graph.ChartDashStyle.Dash;

        chart.ChartAreas["draw"].BackColor = Color.Black;

        // Create a new function series
        chart.Series.Add("MyFunc");
        // Set the type to line      
        chart.Series["MyFunc"].ChartType = Graph.SeriesChartType.Line;
        // Color the line of the graph light green and give it a thickness of 3
        chart.Series["MyFunc"].Color = Color.LightGreen;
        chart.Series["MyFunc"].BorderWidth = 3; 
        //This function cannot include zero, and we walk through it in steps of 0.1 to add coordinates to our series
        for (double x = 0.1; x < MaxX; x += 0.1)
        {
            chart.Series["MyFunc"].Points.AddXY(x, Math.Sin(x) / x);
        }
        chart.Series["MyFunc"].LegendText = "sin(x) / x";
        // Create a new legend called "MyLegend".
        chart.Legends.Add("MyLegend");
        chart.Legends["MyLegend"].BorderColor = Color.Tomato; // I like tomato juice!
        Controls.Add(this.chart);           
    }
}
}

Answer 1

原因是在Form1_Load的末尾，您使用

添加图表

Controls.Add(this.chart);

此将图表限定为类的成员（MSDN），但您尝试在Form1_Load方法范围内声明它。

如果您想在方法中使用声明，则必须将最后一行更改为

Controls.Add(chart);

为什么我必须在Form1_Load方法之外初始化我的图表？ C＃

1 个答案: