当您"正常地将其从工具箱中拖出"时，设计器将为新用户控件生成成员声明，并 * 还 * 将其添加到forms Control集合中。据我所知，您的问题表明您希望在代码中声明您的用户控件变量。如果这是目标，我们必须执行与设计器相同的操作，并将其添加到要将其放入的容器的Controls集合中。

• • 示例**
• 使用代码添加FlowLayoutPanel，然后也在代码中向其添加3个CustomUserControls。*

public partial class MainForm : Form
{
    public MainForm() => InitializeComponent();
    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);

        // Declare a flow layout panel in code.
        // Add it to the main form control collection
        var flowLayoutPanel = new FlowLayoutPanel
        {
            Name = "flowLayoutPanel",
            Dock = DockStyle.Fill,
        };
        this.Controls.Add(flowLayoutPanel);

        for (char c = 'A'; c < 'D'; c++)
        {
            var userControl = new CustomUserControl
            {
                Name = $"userControl{c}",  // No space, start with lowercase
                Text = $"UserControl {c}", // Visible name
                Margin = new Padding(10, 2, 10, 2),
                Width = flowLayoutPanel.Width - 20,
            };
            flowLayoutPanel.Controls.Add(userControl);
        }

        // T E S T
        CustomUserControl? loopback = GetUserControl("userControlA");
        Debug.Assert(loopback != null, "Expecting to retrieve user control by name");
    }

然后，若要使用该控件，请按名称从Controls集合中检索它。

CustomUserControl? GetUserControl(string name)
    {
        var layoutPanel = Controls["flowLayoutPanel"] as FlowLayoutPanel;
        return layoutPanel.Controls[name] as CustomUserControl;
    }
}

其中：

public partial class CustomUserControl : UserControl
{
    public CustomUserControl() => InitializeComponent();
    public new string Text
    {
        get => label1.Text; 
        set => label1.Text = value;
    }
}