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Detailed explanations of some classic ASP.NET issues

零下一度Original: 2017-07-03 16:58:061575browse

　1. In which systems can ASP.NET run?

At present, ASP.NET can only run on Microsoft's Windows 2000, Windows XP and Windows 2003 systems, and requires the support of Microsoft Internet Information Server (IIS). Microsoft originally planned to make Windows NT4. 0 also supports ASP.NET, but Microsoft may have some technical issues or market considerations and has not yet implemented support for ASP.NET under NT.

　2. Can more than one language be used in one ASPX file?

The answer will make you a little disappointed. Although Microsoft provides a common language runtime environment (CLR, Common Laguage Runtime), which achieves tight integration between multiple programming languages, allowing you to A VB object exports the objects required by C#, but only one language can be used in an ASPX file, just as you cannot use C# syntax in VB.NET.

　3. What languages do the server-side scripts of ASPX files support?

Currently, ASPX files only support C#, Visual Basic.NET, Jscript.NET and J#, but if you use the code-behind (code separation) method to create an independent code file, you can use any . NET compiler supports the language to implement the function.

　4. Can code-behind (code separation) technology be used in the Global.asax file?

Of course, for example:
Global.asax:

And use code-behind (code separation) technology

　Global.asax：  
　　  
　　MyApp.vb:  
　　Imports System.Web  
　　Imports System.Web.
Session
State  
　　Public Class MyApp  
　　Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)  
　　Application("online_session") = 0  
　　End Sub  
　　Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs)  
　　Application.Lock()  
　　Application("online_session") = CInt(Application("online_session")) + 1  
　　Application.UnLock()  
　　End Sub  
　　Sub Session_End(ByVal sender As Object, ByVal e As EventArgs)  
　　Application.Lock()  
　　Application("online_session") = CInt(Application("online_session")) - 1  
　　Application.UnLock()  
　　End Sub  
　　End Class

5. Can I See the code that an ASPX file generates in ASP.NET?

As you can see, when your ASPX file contains a command or is declared in Web.config, you can use Microsoft.NET\Framework\v1.0.nnnn\Temporary ASP in the system directory Find the ASPX file generated under ASP.NET in .NET Files.

　6. How to comment in ASPX files?

Same as the method in the ASP file.
　

　7. Can there be more than one server-side Form tag in an ASPX file?

No

8. Can I use custom data types in Web forms

Yes, you can include custom data The DLL file of the type is placed in the BIN directory in the program root directory. ASP.NET will load the DLL file when the data type is referenced.

　9. What events can I trigger in the Global.asax file?
The events triggered when the Application object is created and ended are
Application_Start
Application_End
The events triggered when the Session object is created and ended are
• Session_Start
• Session_End
Right The events triggered when the program has a request are (arranged in order of occurrence)
　•Application_BeginRequest
•Application_AuthenticateRequest
•Application_AuthorizeRequest
•Application_ResolveRequestCache
•Application_AcquireRequestState
•Application_PreRequestHandler Execute
　•Application_PostRequestHandlerExecute
•Application_ReleaseRequestState
•Application_UpdateRequestCache
•Application_EndRequest
The events triggered when an error occurs in a program are
•Application_Error
•Application_Disposed
10. Does the Web control support style sheets? (CSS)?

Yes. All Web controls inherit a property named CssClass from the base class System.Web.UI.WebControls.WebControl. The following example defines a CSS class named Input and uses it to modify a TextBox control to display text in red 10-point Verdana type:

Supported, all Web controls inherit a property called CssClass from the base class System.Web.UI.WebControls.WebControl.
For example:

  
　　 <html>  
    <head>  
    <style>  
    .Input { font: 10pt verdana; color: red; }  
    </style>  
    </head>  
    <body>  
    <form runat="server">  
    <asp:TextBox CssClass="Input" RunAt="server" />  
    </form>  
    </body>  
    </html>

　　　11、在ASPX文件中默认导入那些名称空间？

　　ASPX默认导入的名称空间可以直接引用了，使用其它的名称空间就的自行导入了。

　　默认名称空间
　　 System
　　 System.Collections
　　 System.Collections.Specialized
　　 System.Configuration
　　 System.Text
　　 System.Text.RegularExpressions
　　 System.Web
　　 System.Web.Caching
　　 System.Web.Security
　　 System.Web.SessionState
　　 System.Web.UI
　　 System.Web.UI.HtmlControls
　　 System.Web.UI.WebControls
　　12、我是否可以自己创建服务器控件呢？

　　可以，创作您自己的 ASP.NET 服务器控件很容易。创建简单的自定义控件时，您所要做的只是定义从 System.Web.UI.Control 派生的类并重写它的 Render 方法。Render 方法采用 System.Web.UI.HtmlTextWriter 类型的参数。控件要发送到客户端的 HTML 作为字符串参数传递到 HtmlTextWriter 的 Write 方法。
　　例如：
服务器控件代码（简单显示字符串）：Simple.vb：

 Imports System  
    Imports System.Web  
    Imports System.Web.UI  
    Namespace SimpleControlSamples  
    Public Class SimpleVB : Inherits Control  
    Protected Overrides Sub Render(Output As HtmlTextWriter)  
    Output.Write("<H2>欢迎使用控件开发！</H2>")  
    End Sub  
    End Class  
    End Namespace

引用文件Simple.aspx：

 <%@ Register TagPrefix="SimpleControlSamples" Namespace="SimpleControlSamples" Assembly="SimpleControlSamplesVB" %>  
    <html>  
    <body>  
    <form method="POST" action="Simple.aspx" runat=server>  
    <SimpleControlSamples:SimpleVB id="MyControl" runat=server/>  
    </form>  
    </body>  
    </html>

　　13、如何在ASP.NET程序中发送邮件呢？

　　在ASP.NET程序中发送邮件不再象ASP中那样需要组件的支持了，在.NET的框架基类的System.Web.Mail名称空间内包含的MailMessage和SmtpMail类可以实现这个功能。
　　例如：
　　

Dim message As new Mail.MailMessage  
　　message.From = "web3@163.com"  
　　message.To = "web3@163.com"  
　　message.Subject = "测试"  
　　message.Body = "内容"  
　　Mail.SmtpMail.SmtpServer = "localhost"  
　　Mail.SmtpMail.Send(message)

　　14、我将如何通过ADO.NET读取数据库中的图片并显示它呢？

　　下面举一个从Microsoft SQL Server的PUB数据库读取图片并显示它的例子：
　　下面举一个从Microsoft SQL Server的PUB数据库读取图片并显示它的例子：

  <%@ Import Namespace="System.Data.SqlClient" %>  
    <%@ Import Namespace="System.Drawing" %>  
    <%@ Import Namespace="System.Drawing.Imaging" %>  
    <%@ Import Namespace="System.IO" %>  
    <script language="VB" runat="server">  
    Sub Page_load(Sender as Object, E as EventArgs)  
    dim stream as new MemoryStream  
    dim connection as SqlConnection  
    connection=new SqlConnection("server=localhost;database=pubs;uid=sa;pwd=")  
    try  
    connection.Open()  
    dim command as SqlCommand  
    command = new SqlCommand ("select logo from pub_info where pub_id=&#39;0736&#39;", connection)  
    dim image as byte()  
    image = command.ExecuteScalar ()  
    stream.Write (image, 0, image.Length)  
    dim imgbitmap as bitmap  
    imgbitmap = new Bitmap (stream)  
    Response.ContentType = "image/gif"  
    imgbitmap.Save (Response.OutputStream, ImageFormat.Gif)  
    Finally  
    connection.Close()  
    stream.Clse()  
    End Try  
    End Sub  
    </script>

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