Text =''的含义是什么？ [英] What is the meaning of Text=''.

问题描述

Text =''<％＃Eval（XXXXX）％>''。
的含义是什么/>
有什么区别

 <   asp：标签    ID   =   xxxxxx    runat   =  server   文字  ='  <％  #Eval（  xxxx）％>' >  

和

 <   asp：L abel     ID   =  xxxxxx    runat   =  server   文字  ='  xxxxx' >  

??

解决方案

Eval用于绑定到设置的UI项目是只读的（例如：标签或只读文本框），即Eval用于单向绑定 - 用于从数据库读取到UI字段。



它通常用于后期绑定数据（从开始时不知道），并且通常绑定到包含整个记录的数据绑定控件的最小部分。 Eval方法采用数据字段的名称，并返回一个字符串，该字符串包含数据源中当前记录中该字段的值。您可以提供可选的第二个参数来指定返回字符串的格式。字符串格式参数使用为String类的Format方法定义的语法。

Text =''<％＃Eval（xxxx）％>'' - 标签显示dataSource'''xxxx''字段值。



Text =''xxxx'' - 标签显示字符串''xxxx''

第二个示例将始终将其文本设置为 xxxxx

第一个示例更复杂：它获取属性的值 xxxxx 。因此，如果属性 xxxxxx 设置为Hello，则标签将使用后期绑定显示Hello。通常，这用作模板的一部分（在这种情况下，属性是当前数据的一部分），但是可以在模板外部使用它来绑定到页面/控件的类上的属性。 Eval 是只读的：值从源绑定到控件。有一个类似的方法 Bind 这是双向的，因此属性的值将使用控件的值进行更新。显然你不会使用带有标签控件的 Bind ，因为值不会改变，双向绑定比单向<$ c $有更大的开销。 ç>评估

What is the meaning of Text=''<%# Eval("XXXXX") %>''.
What is the difference between

<asp:Label ID="xxxxxx" runat="server" Text='<%# Eval("xxxx") %>'> 

and

<asp:Label ID="xxxxxx" runat="server" Text='xxxxx'>

??

解决方案

Eval is used to bind to an UI item that is setup to be read-only (eg: a label or a read-only text box), i.e., Eval is used for one way binding - for reading from a database into a UI field.

It is generally used for late-bound data (not known from start) and usually bound to the smallest part of the data-bound control that contains a whole record. The Eval method takes the name of a data field and returns a string containing the value of that field from the current record in the data source. You can supply an optional second parameter to specify a format for the returned string. The string format parameter uses the syntax defined for the Format method of the String class.

Text=''<%# Eval("xxxx") %>'' - label displays dataSource''s ''xxxx'' field value.

Text=''xxxx'' - Label displays string ''xxxx''

The second example will have always have it''s text set to xxxxx
The first example is more complicated: it gets the value of a property called xxxxx. So if the property xxxxxx is set to "Hello", the label will display Hello, using late binding. Most often this is used as part of a template (in which case the property is part of the current data), but it is possible to use it outside a template to bind to a property on the page/control''s class. Eval is read only: the value is bound from the source to the control. There is a similar method Bind which is two-way, so the value of the property will be updated with the control''s value. Obviously you wouldn''t use Bind with a label control as the value won''t change and two-way binding has a greater overhead than the one way Eval

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