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.NET Framework 3.5
 GetCacheDependency Method

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This page is specific to
Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:
.NET Framework Class Library
VirtualPathProvider..::.GetCacheDependency Method

Creates a cache dependency based on the specified virtual paths.

Namespace:  System.Web.Hosting
Assembly:  System.Web (in System.Web.dll)
Visual Basic (Declaration)
Public Overridable Function GetCacheDependency ( _
    virtualPath As String, _
    virtualPathDependencies As IEnumerable, _
    utcStart As DateTime _
) As CacheDependency
Visual Basic (Usage)
Dim instance As VirtualPathProvider
Dim virtualPath As String
Dim virtualPathDependencies As IEnumerable
Dim utcStart As DateTime
Dim returnValue As CacheDependency

returnValue = instance.GetCacheDependency(virtualPath, _
    virtualPathDependencies, utcStart)
C#
public virtual CacheDependency GetCacheDependency(
    string virtualPath,
    IEnumerable virtualPathDependencies,
    DateTime utcStart
)
Visual C++
public:
virtual CacheDependency^ GetCacheDependency(
    String^ virtualPath, 
    IEnumerable^ virtualPathDependencies, 
    DateTime utcStart
)
JScript
public function GetCacheDependency(
    virtualPath : String, 
    virtualPathDependencies : IEnumerable, 
    utcStart : DateTime
) : CacheDependency

Parameters

virtualPath
Type: System..::.String
The path to the primary virtual resource.
virtualPathDependencies
Type: System.Collections..::.IEnumerable
An array of paths to other resources required by the primary virtual resource.
utcStart
Type: System..::.DateTime
The UTC time at which the virtual resources were read.

Return Value

Type: System.Web.Caching..::.CacheDependency
A CacheDependency object for the specified virtual resources.

The default implementation of the GetCacheDependency method returns nullNothingnullptra null reference (Nothing in Visual Basic). To cache virtual resources for later use you must override either the GetCacheDependency method or the GetFileHash method.

The following code example implements the GetCacheDependency method for a custom VirtualPathProvider class. For the full code required to run the example, see the Example section of the VirtualPathProvider class overview topic.

Visual Basic
Public Overrides Function GetCacheDependency(ByVal virtualPath As String, ByVal virtualPathDependencies As IEnumerable, ByVal utcStart As Date) As CacheDependency
  If (IsPathVirtual(virtualPath)) Then

    Dim fullPathDependencies As System.Collections.Specialized.StringCollection
    fullPathDependencies = Nothing

    ' Get the full path to all dependencies.
    For Each virtualDependency As String In virtualPathDependencies
      If fullPathDependencies Is Nothing Then
        fullPathDependencies = New System.Collections.Specialized.StringCollection
      End If

      fullPathDependencies.Add(virtualDependency)
    Next

    If fullPathDependencies Is Nothing Then
      Return Nothing
    End If

    Dim fullPathDependenciesArray As String()
    fullPathDependencies.CopyTo(fullPathDependenciesArray, 0)

    Return New CacheDependency(fullPathDependenciesArray, utcStart)
  Else
    Return Previous.GetCacheDependency(virtualPath, virtualPathDependencies, utcStart)
  End If
End Function

C#
public override CacheDependency GetCacheDependency(
  string virtualPath, 
  System.Collections.IEnumerable virtualPathDependencies, 
  DateTime utcStart)
{
  if (IsPathVirtual(virtualPath))
  {
    System.Collections.Specialized.StringCollection fullPathDependencies = null;

    // Get the full path to all dependencies.
    foreach (string virtualDependency in virtualPathDependencies)
    {
      if (fullPathDependencies == null)
        fullPathDependencies = new System.Collections.Specialized.StringCollection();

      fullPathDependencies.Add(virtualDependency);
    }
    if (fullPathDependencies == null)
      return null;

    // Copy the list of full-path dependencies into an array.
    string[] fullPathDependenciesArray = new string[fullPathDependencies.Count];
    fullPathDependencies.CopyTo(fullPathDependenciesArray, 0);
    // Copy the virtual path into an array.
    string[] virtualPathArray = new string[1];
    virtualPathArray[0] = virtualPath;

    return new CacheDependency(virtualPathArray, fullPathDependenciesArray, utcStart);
  }
  else
    return Previous.GetCacheDependency(virtualPath, virtualPathDependencies, utcStart);
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0
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