asp.net遍历控件的实现
1、在页面动态添加一个控件的方法。在页面的HTML代码上设置一个asp:PlaceHolder 站位控件,当页面被加载的时候,在这个PlaceHolder控件上添加所需要的其他控件。
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2、遍历控件的方法。
页面可以被看成各种控件组成的一个集合。在页面被初始化和加载过程中,可以遍历这些控件,找到特定的控件,或者改变某些控件的属性。
先看下面的一个例子:
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这个例子列出页面上所有的控件,结果如下:
A List of the Controls in the Controls
Collection
System.Web.UI.LiteralControl -
System.Web.UI.WebControls.Label - lblControlList
System.Web.UI.LiteralControl -
System.Web.UI.HtmlControls.HtmlForm -
System.Web.UI.ResourceBasedLiteralControl -
特别要注意的一点:以上代码没有列出ID=“txtName”的TextBox控件!因为这个TextBox控件包含在Form里面,是Form的一个子控件。而我们的代码 foreach(Control c in Controls) 只关心当前页面Controls的控件,至于子控件却未能涉及。(可以把这些控件理解成一个树状的层次关系)
页面Controls
/ | \ //foreach(Control c in Controls)
控件1 控件2 控件3 // 只判断控件1、2、3属于页面Controls
/ \ //而未涉及到下属子控件
子控件1 子控件2
为了真正做到遍历所有控件集,可以用递归的方法来实现:
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以上代码运行结果如下:
A List of the Controls in the Controls
Collection
- System.Web.UI.LiteralControl
- System.Web.UI.WebControls.Label
- System.Web.UI.LiteralControl
- System.Web.UI.HtmlControls.HtmlForm
- System.Web.UI.LiteralControl
- System.Web.UI.WebControls.TextBox
- System.Web.UI.LiteralControl
- System.Web.UI.ResourceBasedLiteralControl
这下TextBox控件真的露出了庐山真面目。
3、动态地创建控件、遍历创建的控件以及改变控件属性的一个应用。
用户输入一个1-10的整数,按按钮后动态创建相应数字的TextBox。代码如下:
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总结: 理解asp.net页面的组成及控件的层次结构,通过递归实现控件遍历。