📄 developapps-saving.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>Adding and Updating data in an EasyObject business object</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">Adding and Updating data in an EasyObject business object</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 common application task is to update or add new data to a business object 
	and then persist that data to the 
	database. For example, a human resources application may need to add new 
	employees to the company, or an employee may have moved requiring an address 
	change. EasyObjects.NET allows the developer to make as many changes 
	locally, then save the changes all at once.</p>
	<h2>Typical Goals</h2>
	<p>In this scenario, you want to retrieve one or multiple rows from a database and 
	load the EasyObject business object with the results, make changes or add 
	new records and then save the changes to the database.</p>
	<p>These goals can be summarized as follows: </p>
	<ul>
		<li>You want to retrieve data for add or update purposes.  
		</li>
		<li>You want to make all the changes locally before saving.  
		</li>
		<li>You want to make one call to save the changes to the database. 
		</li>
	</ul>
	<h2>Solution</h2>
	<p>Use the <b>Save</b> method provided by the <b>EasyObject</b> class. For example, if the application uses a 
	Employees, you might pass a employee ID to the LoadByPrimaryKey method to indicate 
	which employee record to retrieve. Then make the necessary data updates and 
	call the <b>Save</b> method to update the record in the database..</p>
	<p>Alternatively, you can call the <b>AddNew</b> method of the <b>EasyObject</b> 
	class to add a new record to the business object. Fill in all the required 
	fields using the strongly-typed properties and call the <b>Save</b> method 
	to add the record to the database.</p>
	<p>EasyObjects.NET internally maintains the state of each data row, so rows 
	with a <b>DataRowState.Modified </b>call the update logic, while <b>
	DataRowState.Added </b>call the insert logic.</p>
	<h2>Using Save</h2>
	<p>The following code shows how to use the <b>Save</b> method.</p>
	<p>[C#]</p>
<!-- code formatted by http://manoli.net/csharpformat/ -->
<pre class="csharpcode">
Products prod = new Products();

// Update the requested product
prod.LoadByPrimaryKey(4);
prod.UnitsInStock += 1;

// Call AddNew() to add a new row to the EasyObject. You must fill in all 
// required fields or an error will result when you call Save().
prod.AddNew();

// Note the use of the 's_' fields, which take strings as arguments. If this object
// were being loaded from TextBox objects on a WinForm, you don't have to worry about
// the datatype because this is handled for you in EasyObjects
prod.s_ProductName = &quot;EasyObjects&quot;;
prod.s_Discontinued = &quot;True&quot;;
prod.s_QuantityPerUnit = &quot;10&quot;;
prod.s_ReorderLevel = &quot;100&quot;;
prod.s_UnitPrice = &quot;49.95&quot;;
prod.s_UnitsInStock = &quot;200&quot;;

// Only one call to Save() to do the Add and Update
prod.Save();

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

' Update the requested product
prod.LoadByPrimaryKey(4)
prod.UnitsInStock += CType(1, Short)

' Call AddNew() to add a new row to the EasyObject. You must fill in all 
' required fields or an error will result when you call Save().
prod.AddNew()

' Note the use of the 's_' fields, which take strings as arguments. If this object
' were being loaded from TextBox objects on a WinForm, you don't have to worry about
' the datatype because this is handled for you in EasyObjects
prod.s_ProductName = &quot;EasyObjects&quot;
prod.s_Discontinued = &quot;True&quot;
prod.s_QuantityPerUnit = &quot;10&quot;
prod.s_ReorderLevel = &quot;100&quot;
prod.s_UnitPrice = &quot;49.95&quot;
prod.s_UnitsInStock = &quot;200&quot;

' Only one call to Save() to do the Add and Update
prod.Save()
</pre>
	<h2>Usage Notes</h2>
	<!-- 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 + -