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    <p>You can use lazy initialization to postpone the database call until you actually need the information (if ever), and then store the value for re-use.</p> <pre><code>Private _isPowerUser As New Lazy(Of Boolean)(AddressOf GetIsPowerUser) Public Function IsPowerUser() As Boolean Return _isPowerUser.Value End Function Private Function GetIsPowerUser() As Boolean ' Retrieve the information from the database and return Return True Or False End Function </code></pre> <p>In this sample, <code>_isPowerUser</code> is a backing field that uses lazy initialization. It is first initialized when someone calls <code>IsPowerUser</code>. Under the covers, <code>Lazy(Of T)</code> then calls the delegate <code>GetIsPowerUser()</code> that does all the heavy lifting to retrieve the value from the database.</p> <p><code>Lazy(Of T)</code> only needs to call <code>GetIsPowerUser()</code> once. In other words: any consecutive calls to <code>IsPowerUser()</code> do not trigger <code>GetIsPowerUser()</code>.</p> <p><strong>EDIT</strong> (1/2)</p> <p><code>Lazy(Of T)</code> was not introduced until .NET 4, so here is a code sample that works for .NET 2 and above:</p> <pre><code>Private _isPowerUser As Boolean? Private lazyLock As New Object Public Function IsPowerUser() As Boolean If Not _isPowerUser.HasValue Then SyncLock lazyLock If Not _isPowerUser.HasValue Then _isPowerUser = GetIsPowerUser() End If End SyncLock End If Return _isPowerUser.Value End Function Private Function GetIsPowerUser() As Boolean ' Retrieve the information from the database and return Return True Or False End Function </code></pre> <p><strong>EDIT</strong> (2/2)</p> <p>I changed my code sample to work in a multi-user environment:</p> <pre><code>Private _powerUsers As New Dictionary(Of Long, Boolean) Private ReadOnly LazyLock As New Object Public Function IsPowerUser(userId As Long) As Boolean If Not _powerUsers.ContainsKey(userId) Then SyncLock LazyLock If Not _powerUsers.ContainsKey(userId) Then _powerUsers.Add(userId, GetIsPowerUser(userId)) End If End SyncLock End If Return _powerUsers.Item(userId) End Function Private Function GetIsPowerUser(UId As Long) As Boolean ' Retrieve the information from the database and return Return True Or False End Function </code></pre> <p>Usage example:</p> <pre><code> Dim Steven As Long = 454151 If IsPowerUser(Steven) Then Console.WriteLine("Steven is a power user.") Else Console.WriteLine("Steven is a normal user.") End If </code></pre>
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    1. POVB.Net to optimize execution by keeping data other than fetching data from database everytime
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    1. USSteven Liekens
    1. USSteven Liekens
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    1. POVB.Net to optimize execution by keeping data other than fetching data from database everytime
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    1. COThank you very much Steven Liekens for your reply. I am Newbie in VB development. Let me work with your code.
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      1. USRenjith.R
    2. CO@Renjith.R You can't use the `Lazy` type in 3.5, so I added a new code sample.
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      1. USSteven Liekens
    3. COOh thank you so much.... i was about to change the version of .net framework. I was surfing to get more detail about .net version updation. I am asking is there any problem if i am updating my .net version to 4.5 (newer version)
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