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21.5.2 数据列
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C#高级编程（第3版）
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21.5.2 数据列
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2006-10-13 14:41:00
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<div style='float:left;width:49%'>·<a href='100165602.htm'>21.4 快速数据访问：数据读取器</a></div><div style='float:right;width:49%'>·<a href='100165603.htm'>21.5 管理数据和关系：DataSet类</a></div><div style='float:left;width:49%'>·<a href='100165604.htm'>21.5.1 数据表</a></div><div style='float:right;width:49%'>·<a href='100165606.htm'>21.5.3 数据关系</a></div><div style='float:left;width:49%'>·<a href='100165607.htm'>21.5.4 数据约束</a></div><div style='float:right;width:49%'>·<a href='100165608.htm'>21.6 XML模式</a></div></div>
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<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-GB">21.5.2 </span><span style="FONT-FAMILY: 黑体">数据列</span></h3>
<p class="MsoNormal"><span lang="EN-US" style="BACKGROUND: aqua"><a ftel="datacolumns"></a></span><span lang="EN-US" style="BACKGROUND: aqua"><a ftel="DataColumn"></a></span><span lang="EN-US">DataColumn</span><span style="FONT-FAMILY: 宋体">对象定义了数据表中某列的属性，例如该列的数据类型，该列是否为只读，以及其他属性。列可以在代码中创建，或者由运行库自动生成。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">在创建一个列时，给它指定名称是很有用的，否则运行库就会为该列生成一个名称，其格式是</span><span lang="EN-US">Column<em>n</em></span><em><span style="FONT-FAMILY: 宋体">，</span></em><span style="FONT-FAMILY: 宋体">其中</span><em><span lang="EN-US">n</span></em><span style="FONT-FAMILY: 宋体">是一个递增的数字。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">列的数据类型可以在构造函数中提供，也可以通过设置</span><span lang="EN-US">DataType</span><span style="FONT-FAMILY: 宋体">属性来指定。把<span style="LETTER-SPACING: -0.2pt">数据加载到数据表中后，就不能改变列的数据类型了，否则会抛出</span></span><span lang="EN-US" style="LETTER-SPACING: -0.2pt">ArgumentException</span><span style="FONT-FAMILY: 宋体">异常。</span></p>
<p class="MsoNormal"><span style="FONT-FAMILY: 宋体">创建的数据列可以包含表</span><span lang="EN-US">21-3</span><span style="FONT-FAMILY: 宋体">所示的</span><span lang="EN-US">.NET Framework</span><span style="FONT-FAMILY: 宋体">数据类型。</span></p>
<p class="a5" style="MARGIN-TOP: 8.15pt" align="center"><span style="FONT-FAMILY: 黑体">表</span><span lang="EN-US"> 21-3</span></p>
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<p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">Boolean</span></p>
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<p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">Decimal</span></p>
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<p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">Int64</span></p>
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<p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">TimeSpan</span></p>
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<p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">Byte</span></p>
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<p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">Double</span></p>
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<p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">Sbyte</span></p>
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<p class="a4" style="MARGIN-LEFT: 10.7pt"><span lang="EN-US">UInt16</span></p>
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