.net - 如何在自定义 CF 控件中覆盖 Ambient BackColor

Question

我有一个 Compact Framework (3.5) 控件，我希望它具有 SystemColors.Window 的默认颜色，外观类似于编辑控件。我遇到的问题是 Visual Studio (2008) 始终使用 Control 的默认 BackColor 在设计界面上呈现该控件。我假设它是从基本 Control、父级或 Site 的默认背景色中提取它。

任何人都知道如何指定或以其他方式通知 Visual Studio 默认的 BackColor 应该是什么？

public class MoneyInput : Control
{

    public MoneyInput()
    {            
        base.BackColor = SystemColors.Window;
        base.ForeColor = SystemColors.WindowText;
    }

    public override Color BackColor
    {
        get
        {
            return base.BackColor;
        }
        set
        {
            base.BackColor = value;
            Repaint();                
        }
    }

}

这里是我的 DesignTimeAttributes.xmta 文件的相应部分。请注意，正如您在下面看到的那样，我真的不想将默认颜色设置为白色，我只是想让任何工作:

<DesktopCompatible>true</DesktopCompatible>

<Property Name="BackColor">

  <Browsable>true</Browsable>

  <DesignerSerializationVisibility>
    DesignerSerializationVisibility.Visible
  </DesignerSerializationVisibility>

  <DefaultValue>
    <Type>System.Drawing.Color</Type>
    <Value>System.Drawing.Color.White</Value>
  </DefaultValue>

  <Category>Appearance</Category>

  <Description>The background color of the control</Description>

</Property>

只是为了增加一些进展(或缺乏进展)，我向控件添加了一个日志，这样当我将控件放在设计图面上时我可以看到发生了什么。构造函数中对 BackColor 的写入确实生效，并将颜色从 Control 更改为 Window。但是随后设计器基础结构中的某些东西将颜色(通过属性)设置回 Control。这发生在 ctor 之后但在 OnResize 和 OnHandleCreated 之前。现在，如果控件使用正确的值将 BackColor 属性序列化到设计器中，那么它将被安全地设置回去，但设计器不包含默认值。

最后一次编辑，我认为指定枚举(相对于基类型)的默认值语法不正确。我正在使用我在下面发布的解决方案，但它是一个 hack，希望下一个出现的人能够真正解决它。

Answer 1

我仍然希望得到真正的答案，但我会在这里写下我的解决方案:

public class MoneyInput : Control 
{

  // workaround for colors
  private bool _constructed = false;
  private int _handlesCreated; 


  public MoneyInput()
  {
      this.BackColor = SystemColors.Window;
      this.ForeColor = SystemColors.WindowText;
      _constructed = true;
  }

  public override Color BackColor
  {
      get
      {
          return base.BackColor;
      }
      set
      {
          // The logic below is based on:
          //
          // 1.  If not _constructed then we are getting called 
          //      from our ctor and we want the set to happen.
          // 2.  If we do not have a Handle yet then we are 
          //        getting called by the infrastructure that
          //        creates a control.  
          // 3.  At design-time, the VS designer applies the
          //        Ambient color even if we explicitly set 
          //        our own color.  It is supposed to only apply
          //        the Ambient if we have not explictly set
          //        a color.
          // 4.  At runtime we must accept any color changes
          //        that are passed to us.


          // see if VS designer is screwing with us
          bool ignoreColorSet =
              _constructed
              && _handlesCreated == 0
              && RunningInDesigner;


          if (!ignoreColorSet)
          {
              base.BackColor = value;
              Repaint();
          }


      }
  }


  protected override void OnHandleCreated(EventArgs e)
  {
      _handlesCreated++;
      base.OnHandleCreated(e);         
  }

  private bool RunningInDesigner
  {
      get
      {
          // this control is mobile-only so if we are running on full
          //  windows we must be in design mode.  Note that this works
          //  even if we are not Sited yet, where as checking the 
          //  DesignMode property can't be done untl the control has
          //  a Site.
          return (System.Environment.OSVersion.Platform == PlatformID.Win32NT
              || System.Environment.OSVersion.Platform == PlatformID.Win32Windows);
      }
  }

}