📄 developapps-binding.htm

📁 EasyObjects 是ORM的典型应用的例子是学习研究的很好的范例
💻 HTM
字号:
<html>

<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<link rel="stylesheet" type="text/css" href="MSDN.css" />
<title>Databinding and Looping</title>
</head>

<body>

<!--NONSCROLLING BANNER START-->
<div id="nsbanner">
	<div id="bannerrow1">&nbsp;
	</div>
	<div id="titleRow" style="PADDING-RIGHT: 10px; PADDING-BOTTOM: 0px; PADDING-TOP: 0px">
		<h1 class="dtH1">Databinding and Looping</h1>
	</div>
</div>
<!--NONSCROLLING BANNER END--><!--Topic Start-->
<div id="nstext" style="PADDING-RIGHT: 20px; OVERFLOW: auto; TOP: 0px;" valign="bottom">
	<!-- Page Content -->
	<p>A very common task for developers is to bind query results into a 
	databound control, such as a <b>DropDownList</b> or <b>ListBox</b>. For example, 
	an application that needs to load product detail data based on a user 
	selection from a DropDownList. </p>
	<p>Some situations do not lend themselves to databinding, in which case the 
	developer may have to loop through all of the rows in the EasyObject 
	business entity. For example, the developer may need to build a 
	comma-separated list of ID fields. </p>
	<h2>Typical Goals</h2>
	<p>In this scenario, you want to query a database table or view load the EasyObject business object with the results, 
	then bind the EasyObject to the databound control or loop through the 
	results.</p>
	<p>These goals can be summarized as follows: </p>
	<ul>
		<li>You want to retrieve data from a database table or view.   
		</li>
		<li>You want to bind the results to a databound control or loop through 
		the results manually.    
		</li>
	</ul>
	<h2>Solution</h2>
	<p>For databinding, use the <b>DefaultView</b> property provided by the <b>
	EasyObject</b> class. 
	For manual looping, use the <b>MoveNext </b>method. See the sample code below for examples.</p>
	<h2>Using DefaultView</h2>
	<p>The following code shows how to use the <b>DefaultView</b> property.</p>
	<p>[C#]</p>
<!-- code formatted by http://manoli.net/csharpformat/ -->
<pre class="csharpcode">
Employees emp = new Employees();

// Limit the columns returned by the SELECT query
emp.Query.AddResultColumn(EmployeesSchema.EmployeeID);
emp.Query.AddResultColumn(EmployeesSchema.LastName);

// Add an ORDER BY clause
emp.Query.AddOrderBy(EmployeesSchema.LastName);

emp.Query.Load();

// Bind the EasyObject's DefaultView to the DropDownList for display
this.lstEmployees.DataSource = emp.DefaultView;
this.lstEmployees.DataTextField = EmployeesSchema.LastName.FieldName;
this.lstEmployees.DataValueField = EmployeesSchema.EmployeeID.FieldName;
this.lstEmployees.DataBind();

</pre>
	<p>[VB]</p>
<!-- code formatted by http://manoli.net/csharpformat/ -->
<pre class="csharpcode">
Dim emp As Employees = New Employees

' Limit the columns returned by the SELECT query
emp.Query.AddResultColumn(EmployeesSchema.EmployeeID)
emp.Query.AddResultColumn(EmployeesSchema.LastName)

' Add an ORDER BY clause
emp.Query.AddOrderBy(EmployeesSchema.LastName)

emp.Query.Load()

' Bind the EasyObject's DefaultView to the DropDownList for display
Me.lstEmployees.DataSource = emp.DefaultView
Me.lstEmployees.DataTextField = EmployeesSchema.LastName.FieldName
Me.lstEmployees.DataValueField = EmployeesSchema.EmployeeID.FieldName
Me.lstEmployees.DataBind()
</pre>
	<h2>Using MoveNext</h2>
	<p>The following code shows how to use the <b>MoveNext</b> method.</p>
	<p>[C#]</p>
<!-- code formatted by http://manoli.net/csharpformat/ -->
<pre class="csharpcode">
Employees emp = new Employees();
StringBuilder idList = new StringBuilder();

// Limit the columns returned by the SELECT query
emp.Query.AddResultColumn(EmployeesSchema.EmployeeID);

emp.Query.Load();

// Loop through the results, building a comma separated list of IDs
do
{
    idList.AppendFormat(&quot;{0},&quot;, emp.s_EmployeeID);
} while (emp.MoveNext());
</pre>
	<p>[VB]</p>
<!-- code formatted by http://manoli.net/csharpformat/ -->
<pre class="csharpcode">
Dim emp As Employees = New Employees
Dim idList As StringBuilder = New StringBuilder

' Limit the columns returned by the SELECT query
emp.Query.AddResultColumn(EmployeesSchema.EmployeeID)

emp.Query.Load()

' Loop through the results, building a comma separated list of IDs
Do
    idList.AppendFormat(&quot;{0},&quot;, emp.s_EmployeeID)
Loop While emp.MoveNext()
</pre>
	<h2>Usage Notes</h2>
	<p>The <b>MoveNext</b> method returns a Boolean value indicating whether 
	another record is available. If the last record was reached, it will return 
	false.</p>
	<!-- See Also -->
	<h4 class="dtH4">See also</h4>
	<p>
	<a href="developapps-scenarios.htm">
	Key Scenarios</a>
	<!--Footer Start-->
	<div class="footer">
		<br>
&nbsp;<hr>
		<!--Copyright-->
		<p><i>
⌨️ 快捷键说明

复制代码 Ctrl + C
搜索代码 Ctrl + F
全屏模式 F11
切换主题 Ctrl + Shift + D
显示快捷键 ?
增大字号 Ctrl + =
减小字号 Ctrl + -