用户控件包含组合框，但在设计时设置的项不在运行时 [英] Usercontrol contains a combobox, but the Items set at design time are not in the run time

问题描述

我有一个包含文本框和组合框的用户控件。我已经将combobox的Item属性暴露给用户控件的客户端，因此：

  public System.Windows.Forms.ComboBox.ObjectCollection Item 
 {
 get {return baseComboBox.Items; } 
} 
  

我将用户控件添加到窗体，并设置Items列表使用表单设计器中的属性值编辑器。然后我运行应用程序，组合框的下拉列表为空。要确认在设计时添加的项目不在列表中，我在客户端表单中添加了以下两行代码：

  textBox1.Text = userControl1.Items.Count.ToString（）; 
 userControl1.Items.Add（Test item）; 
 

当我重新运行应用程序时，测试框显示计数为0（零）

认为用户控件的实例在设计时被引用是一个不同的实例。在运行时被引用，我在设计时设置用户控件的BackColor属性。当我重新运行应用程序时，用户控件的BackColor是我在设计器中设置的。

任何关于为什么项目的设计时间设置的想法

$ b

  [DesignerSerializationVisibility（DesignerSerializationVisibility.Content）] 
 public ComboBox.ObjectCollection Item {
 get {return baseComboBox.Items; } 
} 
  

I have a user control that contains a textbox and a combobox. I have exposed the combobox's Item property to clients of the user control, thus:

public System.Windows.Forms.ComboBox.ObjectCollection Item
{
    get { return baseComboBox.Items; }
}

I added the user control to a windows form, and set the Items list using the property values editor in the form designer. I then ran the application, and the combobox's drop down list was empty. To confirm that the items added at design time were not in the list, I added the following two lines of code to the client form:

textBox1.Text = userControl1.Items.Count.ToString();
userControl1.Items.Add("Test item");

When I re-ran the application the test box showed a count of 0 (zero), and the drop-down list of the user control contained only "Test item".

Thinking that maybe the instance of the user control being referenced at design time is a different instance from that being referenced at run time, I set the user control's BackColor property at design time. When I re-ran the app, the user control's BackColor was what I had set it to in the designer.

Any ideas on why the design time setting of the Items does not carry over into the run time?

解决方案

You need an attribute:

[DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
public ComboBox.ObjectCollection Item {
  get { return baseComboBox.Items; }
}

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