Question

我试图在程序运行期间创建一个列表，我在createList（）函数中创建了列表并调用了该函数;但是我无法从之后调用的button1_Click（）函数访问该列表。如何从与其创建的功能不同的功能访问创建的列表。

代码摘录：

 public void createlist()
        {

            ListView MainList = new ListView();

            DisplayPanel.Controls.Add(MainList);

            MainList.View = View.Details;
            MainList.GridLines = true;

            MainList.Name = "MainList";
            MainList.Size = DisplayPanel.Size;
            int s1 = DisplayPanel.Size.Height;
            int s2 = DisplayPanel.Size.Width;
            MainList.Anchor = (AnchorStyles.Bottom | AnchorStyles.Right | AnchorStyles.Left | AnchorStyles.Top);

            MainList.Columns.Add("ProductName", 100);
            MainList.Columns.Add("ProductName2", 100);
            MainList.Columns.Add("ProductName3", 100);
            MainList.Columns.Add("ProductName4", 100);

        }

private void button1_Click(object sender, EventArgs e)
        {

            createlist();   //Calls function and creates the ListView

            ListViewItem Source = new ListViewItem("Source", 0);
            Source.Checked = true;
            Source.SubItems.Add("7");
            Source.SubItems.Add("8");
            Source.SubItems.Add("9");

            MainList.Items.AddRange(new ListViewItem[] {Source});

        }

错误：错误CS0103名称＆＃39; MainList＆＃39;在当前上下文中不存在

Answer 1

发生错误是因为MainList不在button1_Click方法的范围中。

有两种方法可以解决这个问题。

将MainList变量放在所有方法之外。这样，MainList变量就在整个类的范围内，这意味着类中的每个方法都可以访问它。

ListView MainList;
public void createlist()
{
    MainList = new ListView();
    DisplayPanel.Controls.Add(MainList);

    MainList.View = View.Details;
    MainList.GridLines = true;

    MainList.Name = "MainList";
    MainList.Size = DisplayPanel.Size;
    int s1 = DisplayPanel.Size.Height;
    int s2 = DisplayPanel.Size.Width;
    MainList.Anchor = (AnchorStyles.Bottom | AnchorStyles.Right | AnchorStyles.Left | AnchorStyles.Top);

    MainList.Columns.Add("ProductName", 100);
    MainList.Columns.Add("ProductName2", 100);
    MainList.Columns.Add("ProductName3", 100);
    MainList.Columns.Add("ProductName4", 100);

}

// your other method should be here...

从createList返回一个值。

public ListView createlist()
{
    MainList = new ListView();
    DisplayPanel.Controls.Add(MainList);

    MainList.View = View.Details;
    MainList.GridLines = true;

    MainList.Name = "MainList";
    MainList.Size = DisplayPanel.Size;
    int s1 = DisplayPanel.Size.Height;
    int s2 = DisplayPanel.Size.Width;
    MainList.Anchor = (AnchorStyles.Bottom | AnchorStyles.Right | AnchorStyles.Left | AnchorStyles.Top);

    MainList.Columns.Add("ProductName", 100);
    MainList.Columns.Add("ProductName2", 100);
    MainList.Columns.Add("ProductName3", 100);
    MainList.Columns.Add("ProductName4", 100);
    return MainList;
}

private void button1_Click(object sender, EventArgs e)
    {

        var listView = createlist();   //Calls function and creates the ListView

        ListViewItem Source = new ListViewItem("Source", 0);
        Source.Checked = true;
        Source.SubItems.Add("7");
        Source.SubItems.Add("8");
        Source.SubItems.Add("9");

        listView.Items.AddRange(new ListViewItem[] {Source});

    }

我推荐第一个解决方案，因为它允许类中的所有方法访问您可能需要的MainList。如果您完全确定不想以任何其他方式访问MainList，请使用第二种解决方案。

Answer 2

MainList（在您的createList（）函数中）只是该函数的局部变量，只能在该函数中使用。为了能够在其他函数中访问它，您需要将其作为类变量。

Answer 3

您需要将此作为该类的成员才能从其他函数访问它。见下文：

class Foo{
    ListView MainList = new ListView();
    public void createlist()
        {

            MainList = new ListView();

            DisplayPanel.Controls.Add(MainList);

            MainList.View = View.Details;
            MainList.GridLines = true;

            MainList.Name = "MainList";
            MainList.Size = DisplayPanel.Size;
            int s1 = DisplayPanel.Size.Height;
            int s2 = DisplayPanel.Size.Width;
            MainList.Anchor = (AnchorStyles.Bottom | AnchorStyles.Right | AnchorStyles.Left | AnchorStyles.Top);

            MainList.Columns.Add("ProductName", 100);
            MainList.Columns.Add("ProductName2", 100);
            MainList.Columns.Add("ProductName3", 100);
            MainList.Columns.Add("ProductName4", 100);

        }

private void button1_Click(object sender, EventArgs e)
        {

            createlist();   //Calls function and creates the ListView

            ListViewItem Source = new ListViewItem("Source", 0);
            Source.Checked = true;
            Source.SubItems.Add("7");
            Source.SubItems.Add("8");
            Source.SubItems.Add("9");

            MainList.Items.AddRange(new ListViewItem[] {Source});

        }
}

C＃修改一个函数中创建的对象

3 个答案: