如何在ASP.NET 2.0中定制Expression Builders
2007-02-20 00:38
393 查看
expressions是asp.net 2.0中的新特色,它可以使你在asp.net的页面里很方便的使用自定义的属性.
在ASPX页里只要使用$符号就可以访问到,你定制的属性了.
例如我们看个例子:
ASPX页面中如下:
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$connectionStrings:Pubs %>" SelectCommand="select * from catalog"></asp:SqlDataSource>
web.config文件中如下:
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<configuration>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<appSettings/>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<connectionStrings>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<add name="Pubs" connectionString="server=localhost;database=getwant;Trusted_Connection=yes"/>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
</connectionStrings>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
</configuration> 因为在web.config中默认就有了connectionStrings的这个节点,所以我们很方便的使用add增加了一个属性Pubs.
而如何自定义我们自己使用的节点呢?例如:<%$ Version:MajorMinor%>可以显示当前环境下asp.net的主版本号和次版本号呢?
如果我们直接在页面中输入上面的表达式,编译器会告诉你,Version并没有被定义,请在expressionBuilders节点中定制.其实这时候就要用到ExpressionBuilder类了.
System.Web.Compilation.ExpressionBuilder 就是expression builders的基类.
我们看看web.config中的设置:
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<compilation debug="true">
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<expressionBuilders>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<add expressionPrefix="Version" type="VersionExpressionBuilder"/>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
</expressionBuilders>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
</compilation>怎么样是不是很简单呢?定义一个expressionPrefix为Version就可以了.
不过有人说那个type后面的是什么意思呢,有VersionExpressionBuilder这个类吗?
其实这个是我们自己继承了ExpressionBuilder的类.
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
public class VersionExpressionBuilder:ExpressionBuilder
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ContractedBlock.gif)
![](http://blog.csdn.net/Images/dot.gif)
{
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public override CodeExpression GetCodeExpression(BoundPropertyEntry entry,object parsedData,ExpressionBuilderContext context)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
![](http://blog.csdn.net/Images/dot.gif)
{
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
string param = entry.Expression;
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
if (string.Compare(param, "All", true) == 0)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
![](http://blog.csdn.net/Images/dot.gif)
{
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
return new CodePrimitiveExpression(string.Format("{0}.{1},{2}.{3}", Environment.Version.Major, Environment.Version.Minor, +
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Environment.Version.Build, Environment.Version.Revision));
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
else if (string.Compare(param, "MajorMinor", true) == 0)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
![](http://blog.csdn.net/Images/dot.gif)
{
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
return new CodePrimitiveExpression(string.Format("{0}.{1}", Environment.Version.Major, Environment.Version.Minor));
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
else
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
throw new InvalidOperationException("User $ Version:All or $ Version:MajorMinor");
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
}这时候我们在ASPX页面中如下设置就可以通过编译了:
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
ASP.NET <asp:Literal ID="Literal1" runat="server" Text="<% $ Version:MajorMinor %>"></asp:Literal>显示的为"ASP.NET 2.0"
把表示式改为:<%$ Version:All %>就会显示为"ASP.NET 2.0,50727.42 "
Expression builders 1 2 - a nice way to assign property values in web controls
http://www.cnblogs.com/cathsfz/archive/2006/12/02/580142.html
在ASPX页里只要使用$符号就可以访问到,你定制的属性了.
例如我们看个例子:
ASPX页面中如下:
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$connectionStrings:Pubs %>" SelectCommand="select * from catalog"></asp:SqlDataSource>
web.config文件中如下:
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<configuration>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<appSettings/>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<connectionStrings>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<add name="Pubs" connectionString="server=localhost;database=getwant;Trusted_Connection=yes"/>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
</connectionStrings>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
</configuration> 因为在web.config中默认就有了connectionStrings的这个节点,所以我们很方便的使用add增加了一个属性Pubs.
而如何自定义我们自己使用的节点呢?例如:<%$ Version:MajorMinor%>可以显示当前环境下asp.net的主版本号和次版本号呢?
如果我们直接在页面中输入上面的表达式,编译器会告诉你,Version并没有被定义,请在expressionBuilders节点中定制.其实这时候就要用到ExpressionBuilder类了.
System.Web.Compilation.ExpressionBuilder 就是expression builders的基类.
我们看看web.config中的设置:
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<compilation debug="true">
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<expressionBuilders>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
<add expressionPrefix="Version" type="VersionExpressionBuilder"/>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
</expressionBuilders>
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
</compilation>怎么样是不是很简单呢?定义一个expressionPrefix为Version就可以了.
不过有人说那个type后面的是什么意思呢,有VersionExpressionBuilder这个类吗?
其实这个是我们自己继承了ExpressionBuilder的类.
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
public class VersionExpressionBuilder:ExpressionBuilder
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ContractedBlock.gif)
![](http://blog.csdn.net/Images/dot.gif)
{
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public override CodeExpression GetCodeExpression(BoundPropertyEntry entry,object parsedData,ExpressionBuilderContext context)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
![](http://blog.csdn.net/Images/dot.gif)
{
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
string param = entry.Expression;
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
if (string.Compare(param, "All", true) == 0)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
![](http://blog.csdn.net/Images/dot.gif)
{
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
return new CodePrimitiveExpression(string.Format("{0}.{1},{2}.{3}", Environment.Version.Major, Environment.Version.Minor, +
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Environment.Version.Build, Environment.Version.Revision));
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
else if (string.Compare(param, "MajorMinor", true) == 0)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
![](http://blog.csdn.net/Images/dot.gif)
{
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
return new CodePrimitiveExpression(string.Format("{0}.{1}", Environment.Version.Major, Environment.Version.Minor));
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
else
![](http://luyu.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
throw new InvalidOperationException("User $ Version:All or $ Version:MajorMinor");
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://luyu.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
}这时候我们在ASPX页面中如下设置就可以通过编译了:
![](http://luyu.cnblogs.com/Images/OutliningIndicators/None.gif)
ASP.NET <asp:Literal ID="Literal1" runat="server" Text="<% $ Version:MajorMinor %>"></asp:Literal>显示的为"ASP.NET 2.0"
把表示式改为:<%$ Version:All %>就会显示为"ASP.NET 2.0,50727.42 "
Expression builders 1 2 - a nice way to assign property values in web controls
http://www.cnblogs.com/cathsfz/archive/2006/12/02/580142.html
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