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19.3.5 ErrorProvider组件
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19.3.5 ErrorProvider组件
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2006-10-13 14:41:00
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<div style='float:left;width:49%'>·<a href='100165536.htm'>19.3.2 CheckBox控件</a></div><div style='float:right;width:49%'>·<a href='100165537.htm'>19.3.3 ComboBox控件与ListBox控件</a></div><div style='float:left;width:49%'>·<a href='100165538.htm'>19.3.4 DateTimePicker控件</a></div><div style='float:right;width:49%'>·<a href='100165540.htm'>19.3.6 HelpProvider组件</a></div><div style='float:left;width:49%'>·<a href='100165541.htm'>19.3.7 ImageList组件</a></div><div style='float:right;width:49%'>·<a href='100165542.htm'>19.3.8 Label控件</a></div></div>
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<div id="text"> <link href="css.css" rel="stylesheet" type="text/css" /><h3 style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 0cm; MARGIN-RIGHT: 0cm; FTEL: 8.15pt"><span lang="EN-US">19.3.5 ErrorProvider</span><span style="FONT-FAMILY: 黑体">组件</span></h3>
<p class="MsoNormal"><span lang="EN-US">ErrorProvider</span><span style="FONT-FAMILY: 宋体">实际上并不是一个控件，而是一个组件。当把该组件拖放到设计器上时，它会显示在设计器下方的组件栏中。当存在一个错误条件时，</span><span lang="EN-US">ErrorProvider</span><span style="FONT-FAMILY: 宋体">可以在控件的旁边显示一个图标。假定有一个</span><span lang="EN-US">TextBox</span><span style="FONT-FAMILY: 宋体">控件用于显示年龄。业务规则是年龄值不能大于</span><span lang="EN-US">100</span><span style="FONT-FAMILY: 宋体">。如果用户试图输入大于</span><span lang="EN-US">100</span><span style="FONT-FAMILY: 宋体">的年龄，就必须通知用户该年龄大于所允许的值，需要改变输入的值。有效值的检查在文本框的</span><span lang="EN-US">Validated</span><span style="FONT-FAMILY: 宋体">事件中进行。如果验证失败，就调用</span><span lang="EN-US">SetError</span><span style="FONT-FAMILY: 宋体">方法，传送引起错误的控件和将该错误告知用户的字符串。然后，一个图标开始闪烁，表示出现了一个错误，<span style="LETTER-SPACING: 0.2pt">用户把鼠标放在该图标上时，会显示错误文本。图</span></span><span lang="EN-US" style="LETTER-SPACING: 0.2pt">19-4</span><span style="FONT-FAMILY: 宋体; LETTER-SPACING: 0.2pt">显示了文本框中输入无效值时出现的图标。</span></p>
<p align="center"><span lang="EN-US"><img height="94" src="19/image004.jpg" width="170" alt="" /></span></p>
<p style="FTEL: 8.15pt" align="center"><span style="FONT-FAMILY: 宋体">图</span><span lang="EN-US"> 19-4</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">可以为窗体上产生错误的每个控件创建一个</span><span lang="EN-US">ErrorProvider</span><span style="FONT-FAMILY: 宋体">，但如果窗体上有很多控件，这就会很麻烦。另一种选择是使用一个</span><span lang="EN-US">ErrorProvider</span><span style="FONT-FAMILY: 宋体">，在验证事件中调用被验证控件的</span><span lang="EN-US">IconLocation</span><span style="FONT-FAMILY: 宋体">方法和一个</span><span lang="EN-US">ErrorIconAlignment</span><span style="FONT-FAMILY: 宋体">枚举值。这个值设置图标在哪里与控件对齐。接着调用</span><span lang="EN-US">SetError</span><span style="FONT-FAMILY: 宋体">方法。如果没有错误，就调用</span><span lang="EN-US">SetError</span><span style="FONT-FAMILY: 宋体">方法，并把空字符串作为它的错误字符串，清除</span><span lang="EN-US">ErrorProvider</span><span style="FONT-FAMILY: 宋体">。下面的示例说明了其工作原理：</span></p>
<p class="2" style="MARGIN-TOP: 8.15pt; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">private void txtAge_Validating(object sender,</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> System.ComponentModel.CancelEventArgs e)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> if (txtAge.TextLength > 0 && Convert.ToInt32(txtAge.Text) > 65)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> errMain.SetIconAlignment((Control)sender, ErrorIconAlignment.MiddleRight);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> errMain.SetError((Control)sender, "Value must be less than 65.");</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> e.Cancel = true;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> else</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> errMain.SetError((Control)sender, "");</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">}</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> </span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">private void txtZipCode_Validating (object sender,</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> System.ComponentModel.CancelEventArgs e)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US">{</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> if (txtZipCode.TextLength > 0 && (txtZipCode.Text.Length != 5)</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> errMain.SetIconAlignment((Control)sender, ErrorIconAlignment.MiddleRight);</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> errMain.SetError((Control)sender, "Must be 5 charactors.");</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> e.Cancel = true;</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> else</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> {</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> errMain.SetError((Control)sender, "");</span></p>
<p class="2" style="MARGIN-LEFT: 21.45pt; FTEL: 18.45pt"><span lang="EN-US"> }</span></p>
<p class="2" style="MARGIN-TOP: 0cm; MARGIN-LEFT: 21.45pt; MARGIN-RIGHT: 0cm; FTEL: 18.45pt"><span lang="EN-US">}</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">如果验证失败</span><span lang="EN-US">(</span><span style="FONT-FAMILY: 宋体">例如</span><span lang="EN-US">txtAge</span><span style="FONT-FAMILY: 宋体">中的年龄超过</span><span lang="EN-US">65)</span><span style="FONT-FAMILY: 宋体">，就调用</span><span lang="EN-US">ErrorProvider</span><span style="FONT-FAMILY: 宋体">组件</span><span lang="EN-US">errMain</span><span style="FONT-FAMILY: 宋体">的</span><span lang="EN-US">SetIcon</span><span style="FONT-FAMILY: 宋体">方法。该方法把图标放在验证失败的控件旁边。接着设置错误，这样，在用户把鼠标放在该图标上时，就会显示一个消息，告知用户哪个控件应为验证失败负责。</span></p></div>
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