ASP.NET 自定义控件从入门到精通4
ASP.NET 自定义控件从入门到精通4
4 使用自定义样式
在上一节中，我们通过集成TableStyle完成了RegistControlStyle类。现在我们需要在RegisterControl中使用自定义的RegistControlStyle。
使用自定义样式，首先复写RegistControl的CreatedControlStyle()方法，代码如下所示：
protected override Style CreateControlStyle()
{
return new RegisterControlStyle(this.ViewState);
}
为什么需要复写CreatedControlStyle属性呢？因为RegisteControl继承与WebControl，所有拥有ControlStyle属性。在WebControl基类中，ControlStyle属性的源代码如下所示：
private Style controlStyle;
public Style ControlStyle
{
get
{
if (this.controlStyle == null)
{
this.controlStyle= this.CreateControlStyle();
}
return this.controlStyle;
}
}
由于自定义控件的ControlStyle属性是通过CreatedControlStyle方法创建的，所以我们需要复写CreatedControlStyle方法，覆盖原有的ControlStyle属性。
现在还需要复写AddAttributeToRender方法，代码如下所示：
[System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand, Name = "FullTrust")]
protected override void AddAttributesToRender(HtmlTextWriter writer)
{
base.AddAttributesToRender(writer);
writer.AddAttribute(HtmlTextWriterAttribute.Id,this.ClientID);
writer.AddAttribute(HtmlTextWriterAttribute.Accesskey,this.AccessKey);
if (!this.Enabled)
{
writer.AddAttribute(HtmlTextWriterAttribute.Disabled,"disabled");
}
writer.AddAttribute(HtmlTextWriterAttribute.Tabindex,this.TabIndex.ToString());
writer.AddAttribute(HtmlTextWriterAttribute.Title,this.ToolTip.ToString());
this.ControlStyle.AddAttributesToRender(writer,this);
IEnumerator item = this.Attributes.Keys.GetEnumerator();
while (item.MoveNext())
{
string key = item.Current.ToString();
writer.AddAttribute(key,this.Attributes[key]);
}
}
公开所有我们需要使用的自定义控件的样式属性，代码如下所示：
public virtual BackImageRepeat BackImageRepeat
{
get
{
RegisterControlStyle rs = this.ControlStyle as RegisterControlStyle;
return rs.BackImageRepeat;
}
set
{
RegisterControlStyle rs = this.ControlStyle as RegisterControlStyle;
rs.BackImageRepeat = value;
}
}
public new BorderStyle BorderStyle
{
get { return (this.ControlStyle as RegisterControlStyle).BorderStyle; }
set { (this.ControlStyle as RegisterControlStyle).BorderStyle = value; }
}
public new System.Web.UI.WebControls.Unit BorderWidth
{
get { return (this.ControlStyle as RegisterControlStyle).BorderWidth; }
set { (this.ControlStyle as RegisterControlStyle).BorderWidth = value; }
}
public int CellPadding
{
get { return (this.ControlStyle as RegisterControlStyle).CellPadding; }
set { (this.ControlStyle as RegisterControlStyle).CellPadding = value; }
}
public int CellSpacing
{
get { return (this.ControlStyle as RegisterControlStyle).CellSpacing; }
set { (this.ControlStyle as RegisterControlStyle).CellSpacing = value; }
}
public string BackImageUrl
{
get { return (this.ControlStyle as RegisterControlStyle).BackImageUrl; }
set { (this.ControlStyle as RegisterControlStyle).BackImageUrl = value; }
}
注意：所有的自定义样式都需要在自定义控件中进行公开，才能被设计器识别。特别需要注意的是，基于自定义样式的属性都要进行转换并且来自于ControlStyle属性。
修改RenderBeginTag()方法，以便使用所有我们公开的自定义控件样式属性。代码如下所示：
public override void RenderBeginTag(HtmlTextWriter writer)
{
writer.RenderBeginTag(HtmlTextWriterTag.Table);
writer.AddAttribute(HtmlTextWriterAttribute.Id,"RegisterTable");
writer.AddStyleAttribute(HtmlTextWriterStyle.Width,"auto");
writer.AddStyleAttribute(HtmlTextWriterStyle.Height, "auto");
writer.AddStyleAttribute(HtmlTextWriterStyle.BackgroundColor,System.Drawing.ColorTranslator.ToHtml(this.BackColor));
writer.AddStyleAttribute(HtmlTextWriterStyle.BorderColor, System.Drawing.ColorTranslator.ToHtml(this.BorderColor));
writer.AddStyleAttribute(HtmlTextWriterStyle.BorderStyle,this.BorderStyle.ToString());
writer.AddStyleAttribute(HtmlTextWriterStyle.BorderWidth,this.BorderWidth.ToString());
writer.AddAttribute("cellpadding",this.CellPadding.ToString());
writer.AddAttribute("cellspacing", this.CellSpacing.ToString());
writer.AddStyleAttribute(HtmlTextWriterStyle.FontFamily,this.ControlStyle.Font.Name);
writer.AddStyleAttribute(HtmlTextWriterStyle.BackgroundImage, (this.ControlStyle as RegisterControlStyle).BackImageUrl);
writer.AddStyleAttribute(this.BackImageRepeat.ToString(),this.BackImageRepeat.ToString());
}
现在我们重新生成解决方案，重新再页面上拖入RegistControl，设定样式属性，效果如图4.1所示：
图4.1 使用自定样式属性控制自定义控件样式
