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[ASP.NET]重构Session确实让代码简洁干净了不少

王朝asp·作者佚名  2006-01-10
窄屏简体版  字體: |||超大  

CodeProject的这篇文章确实对我有所启迪,

http://www.codeproject.com/useritems/SessionWrapper.asp#xx1208856xx

诚如作者所说,我们经常在ASP.NET用许多类似于下面的代码来检测Session中存储的对象,来防止Session过期后存储的变量丢失问题:

Int32 nUserID = -1;

if ( null != Session["userID"] ) {

if ( Session["userID"] is Int32 ) {

if ( 0 < Session["userID"] ) {

nUserID = (Int32) Session["userID"]

}

}

}

if ( -1 == nUserID )

{

throw new ApplicationException ( "Unexpected situation: userID invalid." );

}

this.doSomething( nUserID );

这样的代码会遍布各处。

那么,利用他的这个封装方案来做重构,确实让代码简洁干净了不少!

经过他的封装,上面的代码用这么一句话就行了:

this.doSomething( CCurrentSession.UserID )

他的类其实也很简单,如下所示:

using System;

using System.Web;

/**////--------------------------------------------------------------------

/// Developed by M. van Eijkel - aug 2005

/// [e]: marcelvaneijkel@gmail.com

/// [w]: www.vaneijkel.com

namespace VanEijkel.Web

{

/**//// <summary>

/// Wrapper class for the session object.

/// It centralizes the logic for retrieving and validation of session information.

/// By using an approach like this you improve the protection and encapsulation of existing code.

/// It offers a simple, low-risk, easy manageable way to improve existing WebApplication.

/// Therfore, I call it webRefactoring.

/// </summary>

public class CurrentSession

{

Constants#region Constants

private const String sMANDATORY_SESSION_KEY_NOT_FOUND_MSG = "Session variable excepted but does not exist. Key={0}";

private const String sMANDATORY_SESSION_VALUE_INVALID_NULL = "None null session value excepted. Key={0}";

private const Int32 nUSERID_UNKOWN = -1;

private const Int32 nUSERID_MINIMUM = 1;

private const String sUSERID_INVALID = "Invalid UserID:{0}. UserID should be larger than:{1}";

#endregion

UserID#region UserID

/**//// <summary>

/// Returns the userID as a Int32 instead of an object.

/// This way you will get the compiler protection and intelligence support you need.

/// </summary>

public static Int32 UserID

{

get

{

return (Int32) GetValueOrDefault( eKeys.UserID, nUSERID_UNKOWN );

}

set

{

if ( nUSERID_MINIMUM >= value )

{

throw new ApplicationException ( String.Format(sUSERID_INVALID, value, nUSERID_MINIMUM ));

}

SetValue( eKeys.UserID, value );

}

}

#endregion

private: GetValueOrDefault( eKeys eKey, Object oDefaultValue )#region private: GetValueOrDefault( eKeys eKey, Object oDefaultValue )

/**//// <summary>

/// Gets the value from the session object.

/// </summary>

/// <param name="eKey"> The session key to get the value for.</param>

/// <param name="oDefaultValue">The default value to use if no valid value stored.</param>

/// <returns>When the value is null or the key does not exist,

/// the specified default value is returned.

/// Otherwise, the value is returned</returns>

private static object GetValueOrDefault( eKeys eKey, Object oDefaultValue )

{

//get the value

object oValue = GetValue( eKey );

//value not found or null?

if (null == oValue)

{

//return default value

return oDefaultValue;

}

//everything oke: return session value

return oValue;

}

#endregion

private: GetMandatoryValue( eKeys eKey )#region private: GetMandatoryValue( eKeys eKey )

/**//// <summary>

/// Returns the session value for a session-key that must exist.

/// If the key does not exist an applicationException is thrown.

/// </summary>

/// <param name="eKey"> The session-key to return the session-value for. </param>

/// <returns> A none-null value.</returns>

private static object GetMandatoryValue( eKeys eKey )

{

//get the value

object oValue = GetValue( eKey );

//key not found or value null?

if ( null == oValue )

{

//throw applicationException because its application logic error (none CLR)

throw new ApplicationException ( String.Format( sMANDATORY_SESSION_KEY_NOT_FOUND_MSG, eKey.ToString() ));

}

//everything oke: return value

return oValue;

}

#endregion

private: GetValue( eKeys eKey )#region private: GetValue( eKeys eKey )

/**//// <summary>

/// Gets the session value from the specified key.

/// </summary>

/// <param name="eKey">The key to get the value from</param>

/// <returns>The session value for the specified session key.

/// If the key does not exist, null is returned.

/// </returns>

private static object GetValue( eKeys eKey )

{

return HttpContext.Current.Items[ eKey.ToString() ];

}

#endregion

private SetMandatoryValue( eKeys eKey, Object oValue )#region private SetMandatoryValue( eKeys eKey, Object oValue )

private static void SetMandatoryValue( eKeys eKey, Object oValue )

{

if ( null == oValue )

{

throw new ApplicationException( String.Format(sMANDATORY_SESSION_VALUE_INVALID_NULL, eKey.ToString() ) );

}

}

#endregion

private SetValue( eKeys eKey, Object oValue)#region private SetValue( eKeys eKey, Object oValue)

/**//// <summary>

/// Stores the specified session-value to the specified session-key.

/// </summary>

/// <param name="eKey">The key for the value to store in the session.</param>

/// <param name="oValue">The value to store in the session</param>

private static void SetValue ( eKeys eKey, Object oValue)

{

HttpContext.Current.Items[eKey.ToString()] = oValue;

}

#endregion

/**//// <summary>

/// An enum for the

/// </summary>

private enum eKeys

{

UserID

}

}

}

 
 
 
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