VirtualPathProvider.GetCacheDependency(String, IEnumerable, DateTime) 方法

定义

命名空间:

System.Web.Hosting

程序集:

System.Web.dll

基于指定的虚拟路径创建一个缓存依赖项。

public:
 virtual System::Web::Caching::CacheDependency ^ GetCacheDependency(System::String ^ virtualPath, System::Collections::IEnumerable ^ virtualPathDependencies, DateTime utcStart);

public virtual System.Web.Caching.CacheDependency GetCacheDependency (string virtualPath, System.Collections.IEnumerable virtualPathDependencies, DateTime utcStart);

abstract member GetCacheDependency : string * System.Collections.IEnumerable * DateTime -> System.Web.Caching.CacheDependency
override this.GetCacheDependency : string * System.Collections.IEnumerable * DateTime -> System.Web.Caching.CacheDependency

Public Overridable Function GetCacheDependency (virtualPath As String, virtualPathDependencies As IEnumerable, utcStart As DateTime) As CacheDependency

参数

virtualPath

String

主虚拟资源的路径。

virtualPathDependencies

IEnumerable

一个路径数组，路径指向主要虚拟资源需要的其他资源。

utcStart

DateTime

虚拟资源被读取的 UTC 时间。

返回

CacheDependency

指定虚拟资源的 CacheDependency 对象。

示例

下面的代码示例实现 GetCacheDependency 自定义 VirtualPathProvider 类的方法。 有关运行示例所需的完整代码，请参阅类概述主题的示例 VirtualPathProvider 部分。

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);
        }
    }

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

注解

方法的默认实现 GetCacheDependency 返回 null。 若要缓存虚拟资源供以后使用，必须重写 GetCacheDependency 该方法或 GetFileHash 方法。