What classes are needed to send e-mail from an ASP.NET application?

41. What classes are needed to send e-mail from an ASP.NET application?

The classes MailMessage and SmtpMail have to be used to send email from an ASP.NET application. MailMessage and SmtpMail are classes defined in the .NET Framework Class Library's System.Web.Mail namespace.

42. Why do some web service classes derive from System.Web.WebServices while others do not?

Those Web Service classes which employ objects like Application, Session, Context, Server, and User have to derive from System.Web.WebServices. If it does not use these objects, it is not necessary to be derived from it.

43. What are VSDISCO files?

VSDISCO files are DISCO files that enable dynamic discovery of Web Services. ASP.NET links the VSDISCO to a HTTP handler that scans the host directory and subdirectories for ASMX and DISCO files and returns a dynamically generated DISCO document. A client who requests a VSDISCO file gets back what appears to be a static DISCO document.

44. How can files be uploaded to Web pages in ASP.NET?

This can be done by using the HtmlInputFile class to declare an instance of an <input type="file" runat="server"/> tag. Then, a byte[] can be declared to read in the data from the input file. This can then be sent to the server.

45. How do I create an ASPX page that periodically refreshes itself?

The following META tag can be used as a trigger to automatically refresh the page every n seconds:

<meta http-equiv="Refresh" content="nn">

46. How do I initialize a TextBox whose TextMode is "password", with a password?

The TextBox’s Text property cannot be used to assign a value to a password field. Instead, its Value field can be used for that purpose.

<asp:TextBox Value="imbatman" TextMode="Password"  ID="Password" Runat="server" />

47. Why does the control's PostedFile property always show null when using HtmlInputFile control to upload files to a Web server?

This occurs when an enctype="multipart/form-data" attribute is missing in the <form> tag.

48. How can the focus be set to a specific control when a Web form loads?

1. This can be achieved by using client-side script: document.forms[0].TextBox1.focus ()

2. The above code will set the focus to a TextBox named TextBox1 when the page loads.

49. How does System.Web.UI.Page's IsPostBack property work?

IsPostBack checks to see whether the HTTP request is accompanied by postback data containing a __VIEWSTATE or __EVENTTARGET parameter. If there are none, then it is not a postback.

50. What is WSDL?

WSDL is an XML format for describing network services as a set of endpoints operating on messages containing either document-oriented or procedure-oriented information. The operations and messages are described abstractly, and then bound to a concrete network protocol and message format to define an endpoint. Related concrete endpoints are combined into abstract endpoints (services).

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